Stephen Walt towers over me as we walk in the Harvard sunshine past Eliot Street, a big man who needs to be big right now (he's one of two authors of an academic paper on the influence of America's Jewish lobby) but whose fame, or notoriety, depending on your point of view, is of no interest to him. "John and I have deliberately avoided the television shows because we don't think we can discuss these important issues in 10 minutes. It would become 'J' and 'S', the personalities who wrote about the lobby - and we want to open the way to serious discussion about this, to encourage a broader discussion of the forces shaping US foreign policy in the Middle East."

"John" is John Mearsheimer, a political scientist at the University of Chicago. Walt is a 50-year-old tenured professor at the John F Kennedy School of Government at Harvard. The two men have caused one of the most extraordinary political storms over the Middle East in recent American history by stating what to many non-Americans is obvious: that the US has been willing to set aside its own security and that of many of its allies in order to advance the interests of Israel, that Israel is a liability in the "war on terror", that the biggest Israeli lobby group, Aipac (the American Israel Public Affairs Committee), is in fact the agent of a foreign government and has a stranglehold on Congress - so much so that US policy towards Israel is not debated there - and that the lobby monitors and condemns academics who are critical of Israel.

"Anyone who criticises Israel's actions or argues that pro-Israel groups have significant influence over US Middle East policy," the authors have written, "...stands a good chance of being labelled an anti-Semite. Indeed, anyone who merely claims that there is an Israeli lobby runs the risk of being charged with anti-Semitism ... Anti-Semitism is something no-one wants to be accused of." This is strong stuff in a country where - to quote the late Edward Said - the "last taboo" (now that anyone can talk about blacks, gays and lesbians) is any serious discussion of America's relationship with Israel.

Walt is already the author of an elegantly written account of the resistance to US world political dominance, a work that includes more than 50 pages of references. Indeed, those who have read his Taming Political Power: The Global Response to US Primacy will note that the Israeli lobby gets a thumping in this earlier volume because Aipac "has repeatedly targeted members of Congress whom it deemed insufficiently friendly to Israel and helped drive them from office, often by channelling money to their opponents."

They can say that again. Dore Gold, a former ambassador to the UN, who now heads an Israeli lobby group, kicked off by unwittingly proving that the Mearsheimer-Walt theory of "anti-Semitism" abuse is correct. "I believe," he said, "that anti-Semitism may be partly defined as asserting a Jewish conspiracy for doing the same thing non-Jews engage in." Congressman Eliot Engel of New York said that the study itself was "anti-Semitic" and deserved the American public's contempt.

The Wall Street Journal, ever Israel's friend in the American press, took an even weirder line on the case. "As Ex-Lobbyists of Pro-Israel Group Face Court, Article Queries Sway on Mideast Policy" its headline proclaimed to astonished readers. Neither Mearsheimer nor Walt had mentioned the trial of two Aipac lobbyists - due to begin next month - who are charged under the Espionage Act with receiving and disseminating classified information provided by a former Pentagon Middle East analyst. The defence team for Steven Rosen and Keith Weissman has indicated that it may call Secretary of State Condoleezza Rice and National Security Adviser Stephen Hadley to the stand.

Almost a third of the Journal's report is taken up with the Rosen-Weissman trial, adding that the indictment details how the two men "allegedly sought to promote a hawkish US policy toward Iran by trading favours with a number of senior US officials. Lawrence Franklin, the former Pentagon official, has pleaded guilty to misusing classified information. Mr Franklin was charged with orally passing on information about a draft National Security Council paper on Iran to the two lobbyists... as well as other classified information. Mr Franklin was sentenced in December to nearly 13 years in prison..."

The Wall Street Journal report goes on to say that lawyers and "many Jewish leaders" - who are not identified - "say the actions of the former Aipac employees were no different from how thousands of Washington lobbyists work. They say the indictment marks the first time in US history that American citizens... have been charged with receiving and disseminating state secrets in conversations." The paper goes on to say that "several members of Congress have expressed concern about the case since it broke in 2004, fearing that the Justice Department may be targeting pro-Israel lobbying groups, such as Aipac. These officials (sic) say they're eager to see the legal process run its course, but are concerned about the lack of transparency in the case."

As far as Dershowitz is concerned, it isn't hard for me to sympathise with the terrible pair. He it was who shouted abuse at me during an Irish radio interview when I said that we had to ask the question "Why?" after the 11 September 2001 international crimes against humanity. I was a "dangerous man", Dershowitz shouted over the air, adding that to be "anti-American" - my thought-crime for asking the "Why?" question - was the same as being anti-Semitic. I must, however, also acknowledge another interest. Twelve years ago, one of the Israeli lobby groups that Mearsheimer and Walt fingers prevented any second showing of a film series on Muslims in which I participated for Channel 4 and the Discovery Channel - by stating that my "claim" that Israel was building large Jewish settlements on Arab land was "an egregious falsehood". I was, according to another Israeli support group, "a Henry Higgins with fangs", who was "drooling venom into the living rooms of America."

This was untrue. There was no applause and no accolades and I never stopped "millimetres" short of accusing Israel of these crimes against humanity. The story in the Australian Jewish News is a lie.

So I have to say that - from my own humble experience - Mearsheimer and Walt have a point. And for a man who says he has not been to Israel for 20 years - or Egypt, though he says he had a "great time" in both countries - Walt rightly doesn't claim any on-the-ground expertise. "I've never flown into Afghanistan on a rickety plane, or stood at a checkpoint and seen a bus coming and not known if there is a suicide bomber aboard," he says.

Noam Chomsky, America's foremost moral philosopher and linguistics academic - so critical of Israel that he does not even have a regular newspaper column - does travel widely in the region and acknowledges the ruthlessness of the Israeli lobby. But he suggests that American corporate business has more to do with US policy in the Middle East than Israel's supporters - proving, I suppose, that the Left in the United States has an infinite capacity for fratricide. Walt doesn't say he's on the left, but he and Mearsheimer objected to the invasion of Iraq, a once lonely stand that now appears to be as politically acceptable as they hope - rather forlornly - that discussion of the Israeli lobby will become.

Walt sits in a Malaysian restaurant with me, patiently (though I can hear the irritation in his voice) explaining that the conspiracy theories about him are nonsense. His stepping down as dean of the Kennedy School was a decision taken before the publication of his report, he says. No one is throwing him out. The much-publicised Harvard disclaimer of ownership to the essay - far from being a gesture of fear and criticism by the university as his would-be supporters have claimed - was mainly drafted by Walt himself, since Mearsheimer, a friend as well as colleague, was a Chicago scholar, not a Harvard don.

But something surely has to give.

Across the United States, there is growing evidence that the Israeli and neo-conservative lobbies are acquiring ever greater power. The cancellation by a New York theatre company of My Name is Rachel Corrie - a play based on the writings of the young American girl crushed to death by an Israeli bulldozer in Gaza in 2003 - has deeply shocked liberal Jewish Americans, not least because it was Jewish American complaints that got the performance pulled.

"How can the West condemn the Islamic world for not accepting Mohamed cartoons," Philip Weiss asked in The Nation, "when a Western writer who speaks out on behalf of Palestinians is silenced? And why is it that Europe and Israel itself have a healthier debate over Palestinian human rights than we can have here?" Corrie died trying to prevent the destruction of a Palestinian home. Enemies of the play falsely claim that she was trying to stop the Israelis from collapsing a tunnel used to smuggle weapons. Hateful e-mails were written about Corrie. Weiss quotes one that reads: "Rachel Corrie won't get 72 virgins but she got what she wanted."

Saree Makdisi - a close relative of the late Edward Said - has revealed how a right-wing website is offering cash for University of California at Los Angeles (UCLA) students who report on the political leanings of their professors, especially their views on the Middle East. Those in need of dirty money at UCLA should be aware that class notes, handouts and illicit recordings of lectures will now receive a bounty of $100. "I earned my own inaccurate and defamatory 'profile'," Makdisi says, "...not for what I have said in my classes on English poets such as Wordsworth and Blake - my academic speciality, which the website avoids mentioning - but rather for what I have written in newspapers about Middle Eastern politics."

Mearsheimer and Walt include a study of such tactics in their report. "In September 2002," they write, "Martin Kramer and Daniel Pipes, two passionately pro-Israel neo-conservatives, established a website (www.campus-watch.org) that posted dossiers on suspect academics and encouraged students to report behaviour that might be considered hostile to Israel... the website still invites students to report 'anti-Israel' activity."

Perhaps the most incendiary paragraph in the essay - albeit one whose contents have been confirmed in the Israeli press - discusses Israel's pressure on the United States to invade Iraq. "Israeli intelligence officials had given Washington a variety of alarming reports about Iraq's WMD programmes," the two academics write, quoting a retired Israeli general as saying: "Israeli intelligence was a full partner to the picture presented by American and British intelligence regarding Iraq's non-conventional capabilities."

Rober Fisk, writer for The Independent