Liberal Democrat leader Nick Clegg will argue for a "time-limited" extra tax on the UK's wealthiest people as politicians reconvene after their summer breaks.
The Deputy Prime Minister said the tax, which would be additional to the Liberal Democrats' current mansion tax proposal, was necessary to protect the social cohesion of the country as it continues to battle economic hardship.
"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," Clegg said in an interview with the Guardian.
"In addition to our standing policy on things like the mansion tax, is there a time-limited contribution you can ask in some way or another from people of considerable wealth so they feel they are making a contribution to the national effort?
"What we are embarked on is in some senses a longer economic war rather than a short economic battle."
The Liberal Democrats already have an existing proposal to impose a mansion tax on properties worth more than £2m.
In the interview, Clegg indicated that any new tax would fall on wealth, rather than income, because there are no plans to change the new 45p top rate of income tax.
"The action is making sure that very high asset wealth is reflected in the tax system in the way that it isn't now, making sure that we continue to crack down very hard on tax avoidance, making sure that tax breaks don't go disproportionately to people at the very top," he said.
Clegg will outline proposals for a wealth tax at the party's conference in September.
According to Labour MP, and shadow Treasury minister, Chris Leslie, who is also quoted in the Guardian, 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," he said.
"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."
To aid regulatory reporting
Three year strategic review
Impact on markets
Has run Cautious Managed fund since 2011
What’s right – not what sells