Consumer protection law may have been broken by housebuilders Countryside and Taylor Wimpey, according to the competition watchdog.
The Competition and Markets Authority (CMA) says it has written to the firms outlining specific concerns over their use of terms that double ground rent every 10 to 15 years.
The agency said as a result of the increase, which is built into contracts, it means people can struggle to sell or mortgage their homes, and risk becoming trapped.
The CMA said it is demanding the removal of ground rent terms which officials think are unfair from all existing Countryside and Taylor Wimpey contracts to make sure they are no longer in breach of the law.
Bosses must also agree not to use the terms again in any future leasehold contracts or risk future sanctions.
