“He is abandoning and exploiting poor Londoners to appeal to the far right of the Tory party and Ukip as he forgets London in his desperate scrabble to become leader of his party.”

In contrast, there was near-silence from the Conservatives, with few voices rallying to Johnson’s defence. Asked about the comments, Downing Street would say only that the prime minister believes in social mobility. A Conservative spokesman said the party had nothing to say on the subject.

Johnson’s main defender was former Tory MP Ann Widdecombe, who told the BBC she could not see “what he said that the rest of us couldn’t have worked out at the age of eight or nine”. Later, Conor Burns, a Tory MP and friend of the late Thatcher, praised the speech for being “thoughtful and provocative”.

“I think what Boris Johnson was powerfully and, as ever, controversially, setting out was that we are all born with different talents and abilities, and naturally people are different but it’s up to each and every one of us to strive to maximise what we do with our God-given ability,” he said.

Meanwhile, Labour took the opportunity to claim Johnson’s remarks exposed his true nature. Jon Trickett, deputy chairman of the party, said: “Occasionally the veil slips to reveal the Tories’ inner soul. Today is such a moment when Boris says that greed is a force for social good.”

Johnson’s most provocative comments came when he talked about the relevance of IQ to equality. The mayor said: “Whatever you may think of the value of IQ tests it is surely relevant to a conversation about equality that as many as 16% of our species have an IQ below 85 while about 2% …”

Johnson departed from the text of his speech to ask whether anyone in his City audience had a low IQ: “Over 16% anyone? Put up your hands.”

He then resumed his speech to talk about the 2% who have an IQ above 130, telling the Centre for Policy Studies thinktank: “The harder you shake the pack the easier it will be for some cornflakes to get to the top.”

Johnson also aligned himself with what were seen as the excesses of 1980s Thatcherism as he said: “I stress — I don’t believe that economic equality is possible; indeed some measure of inequality is essential for the spirit of envy and keeping up with the Joneses that is, like greed, a valuable spur to economic activity.”

He made clear, however, that Thatcherism needed to be updated for the 21st century.

“I hope there is no return to the spirit of loadsamoney heartlessness — figuratively riffling banknotes under the noses of the homeless — and I hope that this time the Gordon Gekkos of London are conspicuous not just for their greed — valid motivator though greed may be for economic progress — as for what they give and do for the rest of the population, many of whom have experienced real falls in their incomes over the last five years.”