The scale of the leasehold homes problem is far greater than government figures estimate, according to a campaign group.
Many leaseholders pay excessive ground rent charges of up to £700 a year.
The ministry of housing estimates there were around 4.3m residential leasehold properties in England in 2016.
However, the figure is closer to 6m, taking into account England and Wales there are 6.68m homes, according to campaign group the Leasehold Knowledge Partnership (LKP).
The difference for the gap is because government figures fail to account for many leasehold homes in the social sector, Martin Boyd from LKP told Mortgage Solutions.