The right-hand man to British Prime Minister David Cameron is pitching his Cabinet colleagues on a plan to tax the country's wealthiest more, to offset the impact of a lingering recession.

Liberal Democrat leader and deputy prime minister Nick Clegg told the Guardian newspaper on Wednesday that Britain's finances badly need a one-time emergency tax to be imposed on the country's super-wealthy, or risk a breakdown of social cohesion after social programs were slashed in the recent austerity budget.

Britain's deputy prime minister Nick Clegg proposes a tax on the country's super-rich. (Darren Staples/Reuters)

"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," the Guardian quoted Clegg as saying.

"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."

Although he is not a member of the same Tory party as Prime Minister David Cameron, Clegg rose to prominence in 2010's general election by aligning with the Conservative leader and allowing the latter to form and lead a coalition government.

Clegg pitched the plan to British media on Wednesday, but declined to offer many specifics on how it would work, beyond insisting that it would be one-time only, and target net worth — not high incomes.

Britain's super-wealthy were already targeted for tax hikes in the recent budget, chiefly with a proposed "mansion tax" whenever valuable properties transfer ownership. But that same document nonetheless lowered the top marginal income tax rate to 45 from 50 per cent — a move Clegg supported.

Chancellor of the Exchequer George Osborne and Tory parliamentarian Bernard Jenkin both dismissed the idea on Wednesday, saying it would be a divisive policy that unfairly punishes wealth creators.