AT least 1,000 Hampshire homes will be hit with an average £36,000 bill under plans for a “mansion tax”, it has been claimed.

Labour and the Liberal Democrats are both drawing up proposals to target homeowners with properties valued at more than £2m.

Now the Conservatives have warned the levy would need to raise £36,000 from each wealthy householder, in order to raise the £2billion hoped for.

That is because the Treasury has found there are only 55,000 homes worth more than £2m in Britain – far fewer than the 70,000-75,000 figure cited by Labour and the Lib Dems.

Of those 55,000, around 10,000 are in the south-east region, the figures show – the highest total outside London – with more than 1,000 thought to be in Hampshire.

David Gauke, a Treasury minister, said: “We’ve got the finest minds in the Treasury working on this and they have divided £2billion by 55,000.

“It does not require a huge amount of work – and you end up with an average of £36,000 a year as the annual levy.”

The Conservatives claim that, in order to raise £2billion, supporters of the “mansion tax”

will be forced to apply it to cheaper properties. They also argue it would require homes to be revalued to establish whether they are worth more than the threshold figure – which would be costly and time consuming.

But the Lib Dems hit back at the calculations, pointing out its tax would be on a sliding scale depending on a property’s value – making an average figure “pointless”

Therefore, the owner of a house worth £2.5m would pay £5,000 a year, while a £5m property would face a £30,000 bill.

Some Lib Dems suggest a mansion tax could be a dealbreaking “red line” in talks with the Tories, if the 2015 election resulted in another hung parliament.

A source said: “We would be absolutely delighted to have a political debate about the policy.

“The Conservatives are trying to appeal to about 500 of their wealthy donors. We are trying to appeal to the entire electorate.

This is an incredibly popular policy.”

Labour has not yet announced how much its mansion tax would raise, or whether it would apply to the full value of the property or only the amount above £2m.

It has said it would use the revenue raised to restore the 10p bottom rate of tax abolished by the previous Labour government.