A leaked report on the redevelopment of the Royal Mail site at Mount Pleasant in Clerkenwell reveals that the Mayor plans to charge up to £2,800 per month for 'affordable' flats.
Boris Johnson is expected to grant consent for the development today.
The new site would contain 98 'affordable' rent apartments - with the report suggesting tenants could be charged £1,170 per month for a one bedroom flat, up to £1,690 for a two bedroom and up to £2,800 per month for a four bedroom family home.
The Guardian estimates that a family living in one of the four bedroom flats would need an income of £100,000 to make it affordable.
It's making a complete mockery of the term 'affordable'.
Boris Johnson doesn't really understand social housing in London - or he doesn't care - either way, Londoners are missing out on a great opportunity here for more affordable housing in the middle of London.
More than half of consumers believe Labour's proposals for a mansion tax on properties worth over £2 million are a good idea - but over a third still think the plans are unfair.
The results come from a national survey by Rightmove - who found that 52% supported the proposals while 38% thought it would be a bad idea.
London would be disproportionately hit by the tax if - with 72% of the affected properties in the capital, and a further 16% in the South-East.
Estate agents have criticised the move as effectively being a tax on Londoners who already have to battle with stamp duty charges due to rocketing house prices:
If the mansion tax is introduced, those sellers who have had their homes valued at over £2 million will need to lower their expectations on the deal they'll be able to get, in the same way stamp duty bands affect asking prices.
Whilst it could help raise funds for other causes, according to our survey there are a large proportion of people who wouldn't be affected by it who still think it's unfair.
Boris Johnson is today expected to approve controversial plans to redevelop land at Royal Mail's Mount Pleasant sorting office in North London.
The proposals include hundreds of flats but have been criticised for their low proportion of affordable homes.
The mayor chose to take the final decision away from Islington and Camden councils after a request by Royal Mail.
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Despite working, 48% of 20-to-34 year olds who live with their parents say this is because they can't afford to rent or buy their own home, new Shelter research reveals.
A lack of affordable housing was the single biggest reason why so many young adults in England are unable to fly the nest, a YouGov poll commissioned by the charity found. Additional data from the Census, released to Shelter, showed there are 1.97 million working young adults living with their parents. This accounts for a quarter of all 20-to-34 year old working adults in England.
For the first time ever, the cost of renting in London is double what it costs across the rest of the UK.
New figures from the HomeLet Rental Index show the average rent in the capital is now £1,412, compared to £694 elsewhere.
It also revealed rent in London has increased 11.2% in the last 12 months.
A growing number of businesses in London are being evicted so their buildings can be turned into flats.
It follows a change to the law, which means full planning permission is no longer needed to convert commercial property in new homes.
Some councils are now criticising developers taking advantage of the situation to make a profit from the capital's booming housing prices.
Islington Council's executive member for housing and development, Councillor James Murray, said: "I'm very frustrated by the planning minister's decision to stop us doing what's right for Islington.
"We're already seeing small businesses and charities being evicted from offices to make way for bedsits. People in Islington are losing out on jobs, affordable housing, and any community benefit."
Rents in London have risen 9.4% over the last year.
New figures from the HomeLet Rental Index show the cost of renting in London is increasing five times faster than national average incomes.
It has said the average rent in the capital now stands at £1348 per month