Those agents working in more ordinarily priced areas of the UK might think that mansion tax would not be a worry for them.

But something else could be – a proposal to charge Capital Gains Tax on the sale on private homes.

It has come from Kate Barker, a former member of the Bank of England’s money policy committee, and also author of a report on housing for the last Labout government.

Her new book, Housing: Where’s the Plan?, comes out tomorrow.

Barker said that while Capital Gains Tax is currently charged on second homes, the case for applying it to main residences is strong.

She said:  “Charging CGT on gains on our main residences would bring the taxation of housing more into line with other assets, and it would tend to discourage over-investment in housing.”

She hinted that it might not even be necessary for home owners to sell the property in order to incur Capital Gains Tax.

She said a Capital Gains Tax bill could be rolled up by home owners over their lifetime, and charged on the death of the second partner, alongside inheritance tax.