Plans for a mansion tax are “half-baked” and reform of tax relief could lead to “huge losses” for savers, experts have said of proposed Budget changes revealed by The Telegraph.

Sajid Javid, the Chancellor, is reportedly weighing up limiting tax relief on pension contributions to 20pc and introducing a “recurring” wealth tax on the owners of expensive homes.

However, both proposals have come under fire from commentators.

George Bull of RSM, the accountancy firm, said: “If the Tories introduce a mansion tax they will need to work out how it fits with council tax. Would it replace council tax, which means some of the money raised would have to go to local authorities? Or would you have both, which would be really complicated?

“The real problem is local authority funding and the answer is not clear. These are really big issues and they need proper consultation. A mansion tax in isolation would be half-baked.”

Paul Johnson, the director of the respected Institute for Fiscal Studies think tank, said a mansion tax would be very unpopular. “It wouldn’t be based on a flow of income, as income tax is – the money would just come straight out of your bank account,” he said.