London Mayor - and Conservative MP - Boris Johnson has attacked the city's billionaires for not paying the London Living Wage, comparing them to "orangutans".

Delivering the Sir Simon Milton lecture, the Sun newspaper reported that the outspoken mayor said that the mega rich to do more for their many thousands of workers and meet the £9.15 ($14.25) an hour salary target.

Johnson, whom many see as the next Tory leader and a future Prime Minister, blamed London's 140 billionaires' low pay regimes for creating "vast inequalities of income".

He said: "London is to the billionaire as the jungles of Sumatra are to the orangutans. In fact, we probably have more billionaires than there are orangutans.

"And yet hardly any of them are taking the trouble to ensure that the companies they lead or invest in are paying their employees the London living wage."

The late Sir Simon Milton served as leader of Westminster Council before becoming one of Johnson's deputies.

His foundation helps organisations that want to create "a caring city that offers opportunity for all".