The Liberal Democrats pledged a "radical overhaul" of the tax system which would put £700 in the pockets of millions of taxpayers.
Party leader Nick Clegg set out "the biggest tax switch in generations", proposing to cut income tax bills for those on low and middle incomes.
He said only his party would rebalance the tax system and "make it fair once and for all".
Mr Clegg said taxation under Labour was "complex, unwieldy and most of all unfair" and this had to change.
Top earners would pay their "fair share" to put money in the pockets of those who needed it most, Mr Clegg said.
Liberal Democrats would raise the income tax threshold to £10,000, cutting the average working age person's tax bill by £700 and cutting pensioners' income tax bills by £100.
The £17 billion policy would mean 3.6 million people on low incomes would no longer have to pay income tax, the party claims.
It would be paid for by closing loopholes exploited by the rich, cracking down on tax avoidance, introducing a new mansion tax on homes worth more than £2 million and increasing aviation duties.
The flagship "fairer tax policy" will be at the heart of the party's General Election manifesto, to be launched on Wednesday.
The party also released data showing that Britain's poorest households are paying a greater proportion of their income in tax than in 1997, while the richest people pay less.