Liberal Democrat leader Nick Clegg has criticised the prime minister's unpredictable 'tombola tax system' that does 'enormous damage' to low-income families.
In a speech to the Policy Exchange think-tank, Mr Clegg said: 'Over the course of 11 years of the Labour Government, we have seen National Insurance bumped up, council tax skyrocketing, stamp duty quadrupled, dozens of minor stealth taxes imposed, and now the 10p rate of income tax doubled.
'It is ludicrous that the poorest people still pay a higher proportion of their income in tax than the richest do. It is an immoral use of excessive taxation on those who can afford it least.
'Excessive tax can do enormous damage — especially to the poorest families, whose power in our society is already so limited.
Mr Clegg continued: 'The most disturbing development is the prime minister's penchant for surprise tax changes. It's a tombola tax system. Gordon Brown treats tax like Forrest Gump treats a box of chocolates: you never know what you're going to get.
The Lib Dem leader then turned his attention to the Conservatives' tax policies.
'David Cameron cannot credibly argue that he wants to cuts taxes and improve public services unless he says how. He has asked us to trust him but why on earth should we?
'Tory tax policies are all smoke and mirrors, striking postures whilst ducking all the tough choices.
'He has cried crocodile tears for the millions who lose out from this income tax hike. Crocodile tears because he has no policies to help the people who are suffering.'