Boris Johnson: do those concerned about immigration want ‘forced sterilisation or one-baby policy?’

He said that it was inevitable that immigrants were attracted to London at a time when the economy was growing.

Saying that Russia had a stable population, he went on: "And Russia is a chaotic and nasty place to be."

The Mayor said he did not support uncontrolled immigration, adding: “A state should be able to control its frontiers, I am perfectly prepared to accept that we need proper controls at our borders, and we haven’t had those controls."

But, he asked: "How would people feel if the population pressure was caused entirely by white, Anglo-Saxon Protestant babies?"

Asking if those who favoured population controls would want "forced sterilisation or a one baby policy" - a reference to the practice China used to limit its population - he went on: “I just think there’s a lack of clarity.”

Mr Johnson’s words are in stark contrast to those of the leaders of the main political parties, who have escalated their rhetoric in recent months in response to the electoral threat of the anti-immigration UK Independence Party.

In a major speech on the issue two weeks ago, David Cameron set out plans to reduce access to benefits to immigrants in a bid to reduce the level of migration to the UK.

He promised to negotiate a new settlement with the EU to stop a flood of migrants arriving to take advantage of Britain’s economic success, saying: “Here is an issue which matters to the British people, and to our future in the European Union.

The Mayor also appeared to contradict an article he wrote in The Telegraph just two months ago, in which he suggested that levels of European immigration might need to be capped and urged those concerned about migration to vote Conservative rather than Ukip.

In another sign of division between Mr Johnson, who is hoping to return to Parliament at the forthcoming General Election, and his party leader, the Mayor added that he hoped the Government would ultimately make the “right choice” and back his plan for an airport in the Thames Estuary dubbed “Boris Island.”

He said the expansion of Heathrow had been ruled out, and Gatwick would also prove unsatisfactory, adding: “In the end, having exhausted the alternatives, I do think we will do the right thing and have that airport.”