The climate summit Mayor Bloomberg will host next month could also be his first official meeting with the mayor of London, Ken Livingstone, who has come under attack from Jewish groups in Britain.

Mr. Livingstone, the chairman of C40, a consortium of 40 cities that have banded together to fight climate change, will join dozens of mayors from around the world at the four-day conference. He will deliver an opening address and Mr. Bloomberg and President Clinton will give keynote speeches.

While Mr. Livingstone won reelection handily in 2004 and has strong approval ratings among Londoners, his criticism of Israel has not ingratiated him with many in the Jewish community. In 2005, the mayor compared a reporter from the Evening Standard to “a concentration camp guard” and was accused of anti-Semitism and ordered to serve a one-month suspension. A high court in Britain ultimately vacated the suspension order.

The general counsel for the American Jewish Congress, Marc Stern, stopped short yesterday of saying Mr. Livingstone should be banned from the climate conference, noting that he has devoted a lot of time to the reduction of greenhouse gas emissions. But Mr. Stern called Mr. Livingstone “a noxious character.”

“We can’t object to him being there because he qualifies as the mayor of a major city,” Mr. Stern said. “If one were worried about eliminating political pollution, one would not invite Ken Livingstone — when talking about air pollution, he qualifies.”

A professor at the London School of Economics, Tony Travers, said Mr. Livingstone is no normal politician. He called him a rainbow coalition liberal with a conservative streak on law-and-order issues who dares to say things most politicians would not.

Mr. Travers said the mayor’s concentration camp comment rightly sparked outrage from the Jewish community, but added: “Having watched him for 30 years, I don’t think he is anti-Semitic. I think he has a track record of being anti-racist. I think these remarks tell you rather more about his personal style and his flip use of language than about his underlying views.”

Mr. Livingstone’s office said via email that the mayor believes the Jewish community has “made an incalculable progressive contribution to human civilization” and noted that the high court rejected the accusations of anti-Semitism.

Mr. Livingstone has been leading the pack on environmental issues, most notably with his congestion-pricing program, through which drivers must pay to get into the center of town. The fee, designed to deter people from driving, initially met with resistance, but Mr. Livingstone is now expanding the program.

A survey released by Mr. Bloomberg earlier this week found that London was the cleanest of several major international cities, with residents producing fewer carbon emissions per capita than in New York. But Mr. Bloomberg has been reluctant so far to tackle the political hot potato of congestion pricing here, even as he is pushing to reduce greenhouse gases by 30%.

During a brief stopover in London in March, Mr. Bloomberg did not meet with Mr. Livingstone. An Evening Standard report at the time said Mr. Bloomberg was ducking Mr. Livingstone because of his poor relationship with the Jewish community, but Mr. Bloomberg’s office said he only had a few hours in town.

Yesterday, Mr. Bloomberg’s chief press secretary, Stuart Loeser, said the mayor’s schedule for the week Mr. Livingstone is in town has not been decided yet. He said he did not know whether the two would have a private meeting.