Boris Johnson’s campaign has been funded by a billionaire family behind a development he approved while mayor.
The scheme was labelled unacceptable at the time as there is no social housing.
Labour’s Len Duvall said: It begs the question of whether this is a sign of what’s to come if he enters Downing Street.
Johnson has boasted in his Tory leadership battle he is the man to unite Britain, but the Daily Mirror can reveal as London mayor he signed off a property development with no affordable homes excluding hard-pressed residents.
And the frontrunner’s battle to replace Theresa May was supported by a donation from one of the tycoons he is accused of helping to get the scheme through.
Johnson controversially gave the nod to Westminster council’s recommendation for the £100 million redevelopment of Millbank Tower by the Reuben brothers.
This week, he revealed he has accepted £50,000 in donations from James Reuben.
Planners had suggested a £57million financial contribution in mitigation is an appropriate alternative to affordable homes at the Millbank site, despite there being a chronic shortage of social housing.
Westminster council accepted the maximum reasonable amount of affordable housing in this instance is zero and did not request any compensation.
Neighbouring Lambeth council had reportedly opposed the plans as they contained no affordable homes. But they were approved in April 2016 by Westminster.
It is not known how much the new flats will cost but they are likely to be far out of reach of ordinary Londoners. The average home in the borough is worth more than £1.1million, according to property website Zoopla.
Housing charity Shelter has warned three million new social homes are needed over the next 20 years to fix the crisis.
The numbers being built has fallen from more than 50,000 a year in the mid-90s to less than 10,000 a year since 2015.
Stock fell since the Tories introduced a right for council tenants to buy their homes at a discount, without them being replaced.
The Mumbai-born Reuben brothers, David, 80, and Simon, 77, were named as the second richest people in Britain by the Sunday Times this year, with a £18.7billion fortune.
They made their first billion in Russian metal during the 90s before investing in London property.
Last year, they bought £1billion of property. Simon owns a £55million yacht called Siren and a £22million private jet with David.
James, who is David’s son, donated £25,000 to Boris Johnson on May 30, followed by another £25,000 on June 3.
A spokesman for the Reuben brothers did not respond to a request for comment last night. Their website claims work on the development is due to start this year.
A spokesman for Mr Johnson said at the time of the planning approval: “This development secures the future of a Grade II-listed building, which is of considerable architectural and historic significance to the capital.
The complex not only includes new homes for London, but provides further benefits for the city, with a hotel and cultural facility.