London's mayor has accused the head of the UK's race watchdog of "pandering to the right" so much that "soon he'll be joining the BNP".
"I don't think he does the work," the mayor said of Mr Phillips
Ken Livingstone said Trevor Phillips had "an absolutely disgraceful record" at the Commission for Racial Equality.
He accused Mr Philips of trying to "move the race agenda away from a celebration of multiculturalism".
The CRE said Mr Phillips' views on multiculturalism had been "well-documented" and "well-supported".
Mr Livingstone made his comments after Mr Phillips had rejected a newspaper's description of the weekend's carnival in Notting Hill as "the triumph of multiculturalism".
Mr Phillips had said: "Though it's a fabulous party, carnival can hardly be said to represent the everyday culture of most of London's communities."
The CRE said: "Mr Phillips has used a series of speeches and articles to warn of increasing racial segregation in parts of the UK."
In a speech in London on Wednesday, he said politicians and the media were failing to grasp how society was changing.
Trevor Phillips has warned of increasing racial segregation
"As a result, policy is all too often driven by panic, by political expediency or by whim," he said.
He also warned against calls for the racial profiling of air passengers, saying his commission could use its legal powers to challenge such a scheme.
Mr Livingstone, who has clashed with Mr Phillips in the past, accused him of "trying to move the race agenda away from the celebration of multi-culturalism and pandering to the right".
"I think, I have to say, he has an absolutely disgraceful record", the London mayor told BBC London 94.9.
He went on: "When he was appointed to run the CRE, it did an awful lot of work taking up genuine cases.
"What he did was turn it into a vast press department and wound down all the legal work."
Mr Livingstone claimed Mr Phillips had "denounced" him as a racist during the first London mayoral election in 2000, when he had "a brief sort of black power fling".
"Ever since then he's gone so far over to the other side that I expect soon he'll be joining the BNP," he added.
One paper described the carnival as 'a triumph of multiculturalism'
Responding to Mr Livingstone's criticism, the CRE said: "The CRE's and Trevor's views on multiculturalism have been well documented and are well supported. Obviously, the mayor is entitled to his opinions.
"In terms of our legal work we aim for a responsible and effective approach to enforcement of the Race Relations Act by attempting to resolve issues before taking costly legal action.
"In most cases, organisations respond to our warnings when we notify them that they are potentially breaching the act which is the first part of the enforcement process.
"Alongside taking forward individual cases all those who approach us are given legal advice as far as possible and we also fund grassroots organisations that provide these services on the ground up and down the country."
Mr Livingstone also claimed, in an interview with BBC London 94.9, Mr Phillips felt that "he's achieving something if he's in the papers - and that's not the way it works".
A CRE spokesman said its press team had, in fact, "shrunk in size" to comprise "two press officers, a head of communications and a director".
"Our legal team has grown and consists of 39 officers in England and Wales", the spokesman added.
The former home secretary, David Blunkett, later joined the debate about multiculturalism, telling the BBC it exists in Britain in only a small number of communities.
Last week multiculturalism was openly questioned by ministers launching a new initiative to tackle extremism.
Communities Secretary Ruth Kelly introduced the Commission on Integration and Cohesion with a warning that there was a danger of some communities becoming too isolated.
Mr Blunkett told the World Tonight on Radio 4 that true multiculturalism was confined to parts of London, and a small number of other cities such as Leicester and Bradford.
"We rub up against each other very happily. We work alongside each other, but we're not ourselves and our immediate neighbourhoods multicultural.
"And I think once we get over that barrier we can start talking about multi-ethnicity, we can talk about coping with enormous social change."