The Liberal Democrats would veto a coalition agreement with a minority Conservative government if it tried to drive through £12bn of welfare cuts, Nick Clegg said as he continued to set out his terms for cutting a deal in a hung parliament.

He said David Cameron or Ed Miliband would have to present a “stability Budget” within 50 days of the election incorporating key Lib Dem demands as a price for the party’s support for a power-sharing agreement.

The Deputy Prime Minister said his Budget demand would be a “red line” in negotiations following the election of a hung parliament. He has already said that failure to protect education spending between the ages of two and 19 would be a deal-breaker for his party.

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The budget championed by the Lib Dems would include a timetable to pay off the deficit and ensure the best-off paid more through tax.

Mr Clegg said: “Whether we are in government with Labour or the Conservatives, we will pin them down within weeks of the election and force them to put their cards on the table.

“David Cameron, Ed Miliband – the Liberal Democrats won’t let you bluff your way through, we won’t let you risk our economic recovery.

“We will have a stability budget, to take place within 50 days of election-day, a pre-condition of any coalition arrangement. There will be no deal if there is no stability, no coalition without coming clean with the British people.”

The Lib Dem leader confirmed there was “no way” his party would sign up to Conservative plans to cut the welfare budget by £12bn.

He also said it was inconceivable that the Lib Dems would back a deficit reduction plan which “penalises the working age poor and doesn't ask anything of the wealthiest through the tax system”.