The United Nations human rights investigator for the Palestinian territories said on Tuesday he would not resign and accused critics of calling him anti-Semitic to divert attention from his scrutiny of Israeli policies.

Richard Falk said UN Secretary-General Ban Ki-moon had "joined in the attacks."

UN Watch, an activist group that Falk labels as a "pro-Israel lobbying organization," and Israel's main ally the United States have called for him to quit. U.S. Ambassador Eileen Chamberlain Donahoe described him as "unfit to serve in his role as a UN special rapporteur."

"I don't intend to resign and there doesn't seem to be any formal initiative that is seeking my dismissal," he told a news briefing a day after addressing the UN Human Rights Council.

"My role of trying to speak honestly about the situation that Palestinians are facing under this condition of prolonged occupation generates this sort of reaction that tries to paint anti-Israeli criticism as a form of anti-Semitism," Falk said.

Falk, an American law professor who is Jewish, accused Israel on Monday of imposing collective punishment on 1.75 million Palestinians living in the Gaza Strip and said that the enclave's viability was at stake.

The Israeli and U.S. delegations boycotted the debate at the Human Rights Council where he called for an inquiry into alleged torture of Palestinian detainees in Israel's custody. Israel has stayed away since March 2012, accusing the Geneva forum of bias.

The UN expert, who visited Gaza last December after entering via Egypt, told the council that 70 percent of Gaza's population depended on international aid and 90 percent of the water was "unfit for human consumption."

Falk has long been a controversial figure. After taking up the post in May 2008, he compared Israeli forces' actions in the Gaza Strip to those of the Nazis in wartime Europe.

In December that year he was detained at Ben Gurion Airport and deported by Israeli authorities after being barred from crossing into Palestinian areas to carry out his investigation.

In 2011 he wrote on his blog that there had been an "apparent cover-up" by U.S. authorities over the Sept 11, 2001 attacks. He later said that he meant investigations must be transparent and exhaustive.

That July he posted a cartoon which critics called anti-Semitic. It was later removed and he apologized for "unintentionally posting an anti-Semitic cartoon."

More recently, UN Secretary-General Ban Ki-moon rejected remarks by Falk suggesting the Boston marathon bombings in April were a response to U.S. foreign policy.

'Anti-Semitic card'

Falk, referring to Ban on Tuesday, said: "I have tried to discuss the attacks on me and he has not been willing to see me. In fact, he has joined in these attacks.

"What I believe those forces that have been attacking me are doing, which I think is very unfortunate, is to use the anti-Semitic card as a way of intimidating people who speak honestly about the shortcomings of Israeli policies towards the Palestinians and to make it appear as if criticizing Israel is tantamount to what everybody agrees to be objectionable, which is anti-Semitism," he said on Tuesday.

Falk said that he had received death threats and hate mail over the years but had tried to highlight what had not been understood, particularly in his own country.

"That the occupation is not a neutral reality, but is extremely abusive to the people subject to it, who have endured it for far too long with no end in sight. And that this message needs to be delivered, especially to these citadels of power and influence.