A planning loophole is allowing developers to build thousands of cramped, unaffordable homes in Croydon, a recent report has claimed.

In Croydon 2,727 homes have been delivered through permitted development, a policy which allows buildings to be converted to residential use without going through the full planning process, more than any other borough in London.

Tom Copley, Labour member of the London assembly, argues that by allowing developers to avoid planning regulations, permitted development leads to poor standard homes which fail to meet affordability targets.

In a report titled Slums of the Future, he said: "The need to build more homes in London is clear, but this must not be pursued at the cost of basic standards of quality, and furthermore, not without contributing to the overwhelming need for affordable housing.

"New homes must be properly planned, with oversight from the local authorities, and there is no need for the planning process to be circumvented through permitted development rights to convert office blocks, takeaways or mechanics’ workshops into unsuitable flats.

"If this continues unchecked, and proposals to expand these rights to further use-classes are carried forward, then we will be condemning tens of thousands more Londoners to living in miserable and cramped homes."

AM Copley highlights that 80% of permitted development homes in Croydon were identified as smaller than the minimum size standard enforced by the standard planning process.

In total, 105 homes there are smaller than half the minimum standard, and Urban House on Cavendish Road contains four of the smallest permitted development flats in London, the smallest being just 10 square metres.

Since 2013, nearly 16,000 permitted development homes have been built in London, only 0.4% of which were defined as affordable.

Planning guidance in London seeks a minimum of 35% affordable housing on all new developments in London.

The Government has defended the policy, claiming it frees up developers to deliver the housing needed to resolve the current shortage.

Croydon Council succeeded in blocking permitted development conversions in the town centre in 2014, but they can still take place in other parts of the borough.

Paul Scott, Croydon cabinet member for planning and regeneration, said: "Permitted development has been an absolute disaster.

"The planning system introduced space standards for home for very good reason - to make sure we didn’t end up with these slums.

"Typically young people, who are desperate to buy, are attracted to them, but they find out later that they can’t sell them. People renting are desperate because of the housing crisis.

"It's a cheap, nasty attempt to fix a long-term problem. We need to build many more decent homes."