Boris Johnson has clashed with the Crown Estates over plans to sell 1,300 London homes reserved for key workers, including teachers and nurses in Victoria Park and Lewisham.

The Mayor told the head of the £6.2 billion property portfolio — run on behalf of the Queen for the benefit of the taxpayer — of his grave concerns that a new owner could force up rents.

The row between Mr Johnson and Sir Stuart Hampson, chairman of the Crown Estate, came on the eve of a board meeting at which it is expected to choose a preferred bidder for the homes.

The planned sale, expected to raise about £250 million, is opposed by many tenants on four estates: Victoria Park in east London, Lee Green in Lewisham, Millbank in Pimlico, and Cumberland Market in Camden. The land has been in the hands of the Crown since as early as 1544.

Yesterday the residents’ associations wrote to Sir Stuart accusing the estate of putting profit before its commitment to affordable housing.

The letter says: ”Your reputation for good housing management, built up over nearly a century, is now in rapid decline … we face an uncertain future with a prospective new landlord which we have had no role in selecting and which could see irreparable damage to our communities.”

Richard Blakeway, the Mayor’s housing adviser, said Mr Johnson was concerned about the lack of protection for future tenants. For example the new owner will have the right to put rents up at nine per cent a year.

Currently, tenants of Crown Estate affordable homes only pay about half the level of rent that would be charged by commercial landlords.

Mr Blakeway said: “The Mayor believes the Crown has a duty, as manager of the estate on behalf of the Queen, to ensure homes that are meant to be affordable, remain affordable, and residents’ rights are protected.”

The Crown Estate has said the homes, which generate £3 million a year profit, are “non-core” assets.

A spokesman for the Estate said: “The board is meeting today and the proposal to sell will be considered further. Specifically, the board will be asked to consider whether it wants to select a prospective purchaser from the bids we have received.

“We will communicate the outcome within the next week. Should the board decide to select a prospective purchaser today, no final decision to sell will be taken until further consultation with residents and stakeholders.”