A ‘mansion tax' on all homes worth more than £2m would cost the owners as much as £36,000 a year on average, according to Whitehall analysis.
It is the first time the Treasury has estimated how much would be raised by the tax, which is supported by both Labour and the Liberal Democrats but vehemently opposed by the Tories.
The Times reports that the Treasury has calculated that the charge would apply to 55,000 properties and raise anything between £1.7bn and £2bn.
This means rich homeowners would be hit with an average bill of between £30,000 and £36,000.
Labour adopted the mansion tax, originally drawn up by the Lib Dems, earlier this year. The issue is expected to be a key area of contention ahead of the 2015 general election.
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