Conservative MP Boris Johnson's bid to become London mayor has been condemned by two Labour MPs.
Mr Johnson's campaign team said he 'loathes racism in all its forms'
Dawn Butler and Diane Abbott, Labour MPs for Brent South and Hackney North respectively, said his views on race harked back to the 1950s.
The comments came after the mother of murdered teenager Stephen Lawrence criticised Mr Johnson's bid.
Mr Johnson is on his party's shortlist to become the Tory candidate for the 2008 mayoral election.
Ms Butler highlighted a 2002 article in which Mr Johnson referred to the Queen being greeted in Commonwealth countries by "flag-waving piccaninnies".
She claimed he also said that he expected, during a mooted visit by Tony Blair to the Congo, that "the tribal warriors will all break out in watermelon smiles to see the big white chief".
Ms Butler, whose Brent South constituency is the most ethnically diverse in the UK, said: "These are disgraceful comments that shame Boris Johnson and shame the Conservative Party.
"This is the most offensive language of the colonial past and it shows that the Tory party is riddled with racial prejudice.
"No one with such views can be the mayor of a city with the largest black population in Britain."
Diane Abbott, MP for Hackney North and Stoke Newington, said: "David Cameron is fooling himself if he thinks that Boris Johnson's 1950s attitudes to race will be acceptable to Londoners, both black and white."
But Mr Johnson's campaign team vigorously rejected suggestions that their candidate might be prejudiced, insisting that he "loathes racism in all its forms".
His spokeswoman said: "Boris will be setting out his policies for all Londoners in early September and believes he will be able to convince all Londoners that he is the right choice for them."