Ken Livingstone has warned the government that its policy of merging the Commission for Racial Equality with other bodies could undermine attempts to stamp out racism.
Ministers are planning to merge the CRE with other equalities watchdogs to form a single organisation.
Under the proposed legislation, a new body governing disability, gay and lesbian rights, gender equality and human rights will be established.
But the London mayor suggests that the move could be a serious setback to race relations in the UK.
He warns that the provisions in the Equality Bill fail to give the successor organisation, the Commission for Equality and Human Rights, any security of black and ethnic minority representation.
Livingstone, who is calling on minority groups to lobby against the government, has also intervened to warn the move could mean a reduction in funding for race relations projects.
Under the legislation only spending for disability rights will be ring-fenced, critics of the Bill have warned.
Livingstone says the provisions in the current legislation should not be "acceptable" to black and Asian Londoners.
"Racism is still very real in the UK. The BNP vote grew eight-fold at the last general election," he warned on Monday.
"Given this, it is deeply disconcerting that the government is seeking to establish a new commission that in its current form offers black, Asian and ethnic minorities a poorer deal than that on offer at the existing CRE.
"Those directly affected by discrimination and inequalities should be able to speak for themselves.
"There should be an explicit requirement that there be proper representation. The current proposals could end up creating an equality commission where all the commissioners are white men."
Livingstone insists that a number of CEHR commissioners must be drawn from ethnic minority backgrounds.
