A major international two-day conference on race relations is being over-shadowed by a boycott of the event by London's mayor Ken Livingstone.
Ken Livingstone: Refusing to attend major event
The Commission for Racial Equality convention will host debates on national identity, immigration and segregation in the UK and abroad.
But Mr Livingstone has written to the watchdog's chief Trevor Phillips saying he will not be attending the event.
The mayor's move follows a row over Mr Phillip's views on multiculturalism.
The CRE event was planned to herald the organisation's 30 years of anti-discrimination work - but also the future of community relations under a planned super-watchdog.
Mr Phillips is opening the London event alongside Communities Secretary Ruth Kelly.
Trevor Phillips: Controversial views on segregation
But a number of small anti-racism organisations and individuals have run a boycott campaign since Mr Phillips was named the first head of the incoming Commission for Equality and Human Rights.
That body, to be launched in 2007, merges the CRE with separate watchdogs for sex and disability discrimination.
A spokesman for Mr Livingstone confirmed to the BBC that the mayor had now written to Mr Phillips saying he would be among those not attending the key event.
Instead, London's City Hall, the mayor's headquarters, would be given over on Monday evening to a smaller event on race and faith organised by groups not attending the CRE convention.
The mayor would have been expected to attend because London, one of the most ethnically diverse cities in the world, has been at the heart of debate over community relations since the 2005 London bombings.
In September, Mr Livingstone accused Mr Phillips of "pandering to the right" so much that "soon he'll be joining the BNP".
Much of the criticism of Mr Phillips relates to statements he has made since the London bombings, including his controversial warning that Britain is "sleepwalking towards segregation".
Mr Phillips has defended his views as a realistic attempt to debate difficult issues rather than sweep them under the carpet. The CRE has also dismissed his critics as opposing efforts to move race relations from the margins of society to the mainstream of politics.
The two-day conference will hear from a wide range of high profile speakers from the UK and abroad.
It includes a number of provocatively-titled workshops on race relations. One session entitled "Rivers of blood: Did Enoch Powell get it right?" has been cancelled, even though it appeared in an earlier version of conference literature.