The change would significantly impact people investing in buy-to-let properties and holiday homes.
CGT could rise to 40 or 45 per cent, in line with the higher income tax rate, under the plans being considered, The Sunday Times reported.
It is currently levied at 28 per cent on additional properties.
The mooted rise is one of several possible changes to taxation that could be introduced in a budget in November to help shore up the nation’s finances.
The UK national debt grew to a record high of £2.004trn in July, according to the Office for National Statistics.
The aim is to raise an extra £20bn to £30bn a year.
Other tax rises in the frame are simplifying Inheritance Tax on estates and a hike in Corporation Tax.
There was no indication that HM Treasury is considering extending the current stamp duty holiday beyond 31 March 2021.
Mortgage Solutions has contacted HM Treasury for comment.