Nick Clegg has called on Britain's wealthiest to make an "extra contribution" to the "national effort" of economic recovery.
In an interview with the Guardian, the Deputy Prime Minister suggested people of "very considerable personal wealth" could make a "time limited contribution" as the country faced a "longer economic war".
The Lib Dem leader is expected to flesh out his thoughts on a possible "wealth tax" at the party's autumn conference in Brighton next month, according to the report.
Mr Clegg told the newspaper: "If we are going to ask people for more sacrifices over a longer period of time, a longer period of belt tightening as a country, then we just have to make sure that people see it is being done as fairly and as progressively as possible.
"While I am proud of some of the things we have done as a Government I actually think we need to really hard-wire fairness into what we do in the next phases of fiscal restraint.
"If we don't do that I don't think the process will be either socially or politically sustainable or acceptable."
His comments appear to indicate a renewed plan to better differentiate his party's economic approach within the Coalition with Prime Minister David Cameron's Conservatives.
Mr Clegg added: "If we want to remain cohesive and prosperous as a society, people of very considerable personal wealth have got to make a bit of an extra contribution."
Commenting on the interview, Chris Leslie, Labour's shadow treasury minister, said: "Nick Clegg is once again taking the British people for fools.
"He talks about a tax on the wealthiest, but he voted for the tax cut for millionaires in George Osborne's Budget.
"And he has supported a failing economic plan which has pushed Britain into a double-dip recession and is leading to borrowing going up by a quarter so far this year."