The chancellor's Budget shows he is "in denial" about the scale of cuts needed to address the deficit, Lib Dem leader Nick Clegg has said.
Chancellor Alistair Darling had failed to deliver either "honesty on spending" or "fairness on taxation", he said.
Much was "insubstantial waffle" not specific details of how money would be saved, Mr Clegg claimed.
"This is not a preface to a new government but a footnote to 13 years of failure," he said.
Mr Clegg said only his party was being honest about how it would save money and accused both Labour and the Conservatives of lacking "the courage to come up with details of the cuts we will need in the years ahead to tackle Britain's deficit".
"Neither is being straight with the British people about the tough times ahead. This Budget was a Budget in denial about the scale of change needed."
He said Mr Darling's Budget was "built on growth figures that are unlikely to materialise" and on "false comfort from a small drop in borrowing that doesn't affect the structural deficit".
"We are still borrowing £450m every single day, above all it's a Budget in denial about the unavoidable cuts and savings ahead."
He cannot bury his head in the sand over this just to hide the truth about how long it will take to reduce the deficit
He said Mr Darling had claimed to have identified billions of pounds of savings but had only given "insubstantial waffle" about efficiency savings and a "tiny saving" by relocating civil servants outside London.
He said the chancellor had only slightly adjusted his "wildly over-optimistic" growth forecasts for 2011, to 3-3.5%, against a "consensus everywhere else" of 2%.
"He cannot bury his head in the sand over this just to hide the truth about how long it will take to reduce the deficit."
And Mr Darling was "living in fantasy land" boasting about money saved on unemployment costs - which brought budget deficit predictions down from £178bn to £167bn.
Mr Clegg added: "This government still came in £167bn over budget last year. We aren't better off. We are just ever so slightly less worse off."
The Budget had been silent on the need for more affordable housing and the failure to get banks lending again, he said.
"After 13 years of Labour, Britain is ready for something different as we stand on the brink of an election campaign where everything is to play for.
"My message is simple. This Budget is the old politics and the old politics is not good enough any more. It's time for honesty in spending and fairness in taxes."
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