The Competition and Markets Authority (CMA) said it would examine the scandal surrounding new-build homes sold on leases that were subject to substantial increases in ground rents and the charging of “permission fees” for home improvements. Developers and freeholders could face legal action if the watchdog finds evidence of leasehold mis-selling. The watchdog said it would decide whether the practices constituted “unfair terms”, a breach of consumer contract law.

James Brokenshire, the housing minister, has previously called on the CMA to use its influence to tackle the “culture of consumer exploitation rife in the housing industry” with an inquiry into the estimated 100,000 homes sold with “extortionate” leases.

However, in November, the CMA told the minister it would not investigate the issue, citing the legal complexities surrounding historic cases of mis-selling. In a letter seen by The Times, the watchdog also noted it does not have the power to fine companies using its consumer powers and blamed Brexit preparations for it not being able to prioritise problems in the housing industry.

The U-turn comes after the Commons housing committee published a damning report on the scandal in March, calling for the law to be changed to help people stuck in leasehold properties with crippling fees that they are unable to sell on. It also criticised solicitors for failing to warn clients about the unfair deals, accusing some of being too close to developers.

The leasehold scandal emerged as developers began to sell houses on leasehold rather than freehold, often without the buyer fully understanding the contracts. In many cases the freeholds were bought by offshore investors who demand large sums from homeowners to buy out the contracts.

Taylor Wimpey, one of Britain’s biggest housebuilders, has set aside £130 million to help its customers escape unfair leases it sold. More than 40 property developers and freeholders this year signed a government-backed pledge to help homeowners affected by the scandal by changing the terms of leases for those with onerous clauses.

Sebastian O’Kelly, of the Leasehold Knowledge Partnership, said: “We welcome the CMA looking into this. It’s long overdue and will be welcomed by the 12,000 owners of new leases with doubling ground rents, and 88,000 where the ground rent is above 0.1 per cent of the sale price and whose properties are unsellable.”

The investigation comes as the industry attempts to improve its public image after criticisms of build quality as well as punitive hidden charges.

Countryside Properties this week became embroiled in a row with Joe Anderson, the mayor of Liverpool, who reportedly told residents he would ban the housebuilder from building in the city due to historic cases of selling leasehold homes with “doubling clauses” for ground rents.