The senior diplomat who withdrew as one of Barack Obama's top intelligence officials in a row over Israel has stepped up his attack on those he says are stifling debate in the United States, adding that he was "deeply insulted" to be accused of antisemitism for criticising what he described as "the Israel lobby".

Chas Freeman, a former US ambassador to Saudi Arabia, told CNN that organisations representing the right wing of Israeli politics had "a hammer lock on both public discussion and policy", and that their campaign to force his withdrawal as the chair of Obama's national intelligence council had been intended to "reinforce the taboo against any critical discussion of Israeli policies".

Freeman also reiterated his view that American policy on Israel had contributed to the 9/11 terrorist attacks, part of a litany that prompted several members of Congress to speak out against his appointment. The US was "paying a price" for its Middle Eastern policies, he said, "because our actions have catalysed - perhaps not caused, but catalysed - a radicalisation of Arab and Muslim politics that facilitates the activities of terrorists with global reach, like those who struck us on 9/11."

His opponents "should probably be called the Likud lobby" rather than the Israel lobby, he added. "The atmosphere is such in this country now that, whereas Israelis in Israel routinely criticise Israeli policies that they think may prove to be suicidal for their country, those who criticise the same policies here, for the same reasons, are subject to political reprisal."

Freeman's Washington critics, including the American Israel Public Affairs Committee and the Zionist Organisation of America, have pointed to the fact that he served as president of a thinktank part-funded by the Saudi government, and on the advisory board of a Chinese-owned oil firm.

"If you're going to be an intelligence man, you can't have a financial conflict of interest with countries that are critical to your evaluation of intelligence data," Morton Klein, president of the ZOA, said.

Klein rejected the notion that American debate on Arab-Israeli policy was artificially narrow. "Many people are talking about the establishment of a Palestinian state, and Obama just increased aid to the Palestinian Authority from $700m under Bush to $900m now. What's narrow is that nobody talks about how the PA obligated themselves at Oslo to get rid of incitement to hatred and murder."

Freeman has also been attacked for his alleged support of China in the 1989 Tiananmen Square massacre. In his CNN interview, he insisted that a much-quoted email list posting had been edited to obscure the fact that he was characterising "the dominant view of the Chinese leadership", not his own.

Answering charges of antisemitism, Freeman said: "There's a very large number of American Jews who have written to me to express their gratitude for me raising the issues I have... The last thing on earth I am is antisemitic."