Jewish community leaders are pressuring the police to act against controversial Islamic cleric Yusuf Al-Qaradawi.
The cleric's visit has been backed by London Mayor Ken Livingstone
The Board of Deputies of British Jews has met senior Scotland Yard officers to present a "dossier" of alleged comments by the sheikh.
They say the Egyptian-born cleric is a threat to race relations because he has defended Palestinian suicide bombings in Israel.
But his supporters say his views are being totally distorted.
On Friday, it emerged that Henry Grunwald QC, president of the Board of Deputies of British Jews, had met senior officers at Scotland Yard to present a "dossier" of comments allegedly made by the Sheikh.
Jerry Lewis, deputy president of the board, said the community was concerned the cleric's comments could incite Islamist extremists to acts of violence.
Henry Grunwald: Jewish complaints to the police
He said Jews were particularly concerned because two British men had last year become the first non-Palestinian suicide bombers.
"We have striven and continue to strive to improve relations with the Muslim community in this country. We are determined that they should benefit from our experience.
"The Muslim community is moderately inclined. It's a shame that a few extremists from time to time create problems for the wider Muslim community.
"Sheikh Al-Qaradawi does not differentiate between Jews and Israelis," said Mr Lewis.
He confirmed this had been the first time the Board of Deputies had formally complained about the cleric, even though he had visited London before.
Sir John Stevens, Commissioner of the Metropolitan Police, confirmed complaints had been received.
"We are monitoring what he has said and are ensuring that these comments are taken directly to the Crown Prosecution Service," said Sir John.
"The anger that was created by the comments made by the individual is considerable. I have had personal telephone calls from eminent members of the Jewish community."
Sheikh Al-Qaradawi, a respected thinker in the Middle East, is in London for a series of conferences, including an event looking at how to improve the integration of Muslims in Europe.
On Friday he attended Friday prayers at London's Regent Park Mosque.
Outside a lone gay protester demanded Sheikh Al-Qaradawi be "kicked out" of the country.
Alisdair Hickson, 41, said: "He has expounded views of hatred which encourage violence and homophobia against gay people."
The Metropolitan Police said the Sheikh had pulled out of another event, an education conference sponsored by the force.
A Scotland Yard spokesman said: "As Dr Al-Qaradawi is not speaking at the conference we have decided to continue sponsoring this event.
"To withdraw support at this late stage could damage our partnership with the Muslim community in London and its involvement in helping us to tackle and prevent criminal activity."
But Hasan Mueenuddin, spokesman for Sunday's conference in Wembley, north-west London, said: "I am certain that he is going to speak at the conference."
In an interview with the BBC's Newsnight programme, Sheikh Al-Qaradawi said he believed Palestinian suicide bombings in Israel could be justified because it was a weapon of last resort for a people with no other means to defend themselves.
In that context, he said, the attacks could be considered "martyrdom in the name of God".
A spokesman for the Muslim Council of Britain said the Sheikh's views had been distorted and he had been the victim of an "orchestrated campaign".
"We do not condone the taking of innocent life by anybody in the Middle East, whether they be Israelis or Palestinians" he added.
The cleric has said he is surprised at the controversy his visit and stance have generated.
"For over a third of a century I have been visiting London.
"London is an open city, so why is there this row when I visit London today?" he asked.