The rich could face a levy on the value of their homes as the price of scrapping the top rate of income tax, Business Secretary Vince Cable has suggested.
Mr Cable revived the prospect of imposing a so-called "mansion tax" on properties worth over £2m which he originally proposed when the Liberal Democrats were in opposition.
Interviewed by the BBC, he indicated that it could be the price of Lib Dem support for Chancellor George Osborne's review of the 50p top rate of tax announced in the Budget last week.
"It needs to be a change which is fair overall and does take account of the fact that the wealthy have got to pay their share," Mr Cable said.
"And the emphasis may well have to shift from high marginal rates of tax on income which are undesirable, to taxation of wealth, including property.
"There is a very strong argument that you need to have a proper base for taxing property.
"I'm sure that's one of the things we're going to have to look at as we change away from these very high marginal rates.
"Certainly what I and my Liberal Democrat colleagues will want to see is a very strong commitment to fairness in taxation - and that means lifting low earners out of tax which is what we have done in this Budget - but also making sure that people who are very wealthy and very privileged do pay their share."
The proposition it unlikely to go down well with Conservative MPs who attacked the idea when Mr Cable first proposed it before the general election led to the formation of the coalition Government.