Foreign secretary, Robin Cook, will today attack the Conservatives over the issue of race and defend multiculturalism in a speech to London's Open Society.

Cook will dismiss the idea of Britishness or of the British defined as an ethnically pure race as "a fantasy" and praise immigration as "necessary and desirable". As an illustration of the way in which the UK adapts and absorbs external influences, he will recognise chicken tikka massala as "Britain's true national dish".

The Guardian claims three Conservative MPs have refused to sign up to the Commission for Racial Equality code of practice pledging not to make race a political issue.

Attacking the Conservatives, he will argue that William Hague's recent speech that a Labour second term would turn the UK into a "foreign land" encourages racism in the Conservative Party.