The Liberal Democrats have unveiled plans for a tax on owners of £1m-plus properties to free low-paid workers and pensioners of income tax duties.
Speaking at the party conference in Bournemouth, Treasury spokesman Vince Cable proposed a 0.5% annual levy on Britain's most expensive homes.
The proceeds would help support plans to abolish taxation for four million people who earn less than £10,000.
"It would be dishonest and unbelievable for me to say that taxes overall should never rise," he said. "But the Liberal Democrats' starting point is to aim for fairer not higher taxes."
The debate over the scale of spending cuts and tax increases has dominated Westminster over the past few months, with a verbal slanging match frequently erupting between the main parties.
Cable scorned the Conservatives for posturing over spending cuts without revealing any details, while contrasting his own party's "open" and transparent approach.
He said income tax cuts for those on low and middle incomes would be paid for by closing tax loopholes enjoyed by the relatively wealthy, including the "exceptionally generous" tax relief on large pension pots.
The Lib Dems would also crack down on the "blatant abuse" of tax havens.
The warning comes on the day the BBC Panorama programme alleges the Lloyds Banking Group, which is 70% owned by the UK taxpayer, is being investigated for encouraging wealthy clients to dodge paying UK tax.
Proposing a radical overhaul of the tax landscape to encourage work, savings and innovation, Cable said that the governing party should aim to shift the tax burden from income onto pollution, financial transactions of dubious social and economic value and land values.
He also turned on Gordon Brown, calling his Labour government "exhausted" and cited his "pathetic" efforts to deal with the excessive pay and bonuses of bankers.
To tackle the biggest economic challenges since World War II, Cable argued that a British version of the European Investment Bank or US President Barack Obama's US Investment Bank was needed to match demand for long-term investments with big infrastructure projects necessary for a sustainable green economy.
"Britain's economic heart attack has been traumatic and life threatening, but it also serves as a warning to change lifestyles in a radical way," he said.
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