David Cameron and Ed Miliband have been put on the spot over their economic plans, as the Conservative leader denied he wants to cut benefits for children and his rival in the race for 10 Downing Street said he did not accept Labour overspent when it was last in power.

The pair were speaking on a Question Time general election leaders' special on BBC1, where they and Nick Clegg were separately answering questions from a studio audience in a format devised after Mr Cameron refused to take part in a head-to-head encounter with his Labour rival.

With the May 7 election apparently heading for a hung Parliament with Scottish National Party holding the balance of power, Mr Miliband said he would rather not have a Labour government than form one on the back of a deal with Nicola Sturgeon's party.

"If the price of a Labour government is a coalition or a deal with the SNP, it is not going to happen," said the Labour leader.

The programme came shortly after Liberal Democrats revealed proposals discussed under the coalition for £8 billion cuts to child benefit, including means-testing payments, removing them from 16-to-19-year-olds and limiting the benefit and child tax credit to two children per family, which Treasury Chief Secretary Danny Alexander suggested gave an indication of Tory plans after the May 7 election.

Mr Cameron said: "I don't want to do that. This report that was out today is something I rejected at the time as Prime Minister and I reject again today."

Asked if this was an "absolute guarantee" not to cut child benefit or child tax credit, the Conservative leader said: "Child tax credit we increased by £450.That's not going to fall. Child benefit, to me is one of the most important benefits there is. It goes directly to the family - normally to the mother - £20 for the first child, £14 for the second.

"It is the key part of family's budgets in this country. That's not what we need to change."

Meanwhile, an audience member directly asked Mr Miliband: "Do you accept that when Labour was last in power it overspent?"

The Labour leader replied: "No, I don't. I know you may not agree with that, but let me just say very clearly - there are schools that have been rebuilt in our country, there are hospitals that have been rebuilt, there were SureStart centres that were built that wouldn't have happened.

"There was a global financial crisis which caused the deficit to rise. President Obama isn't dealing with a high deficit because we built more schools and hospitals. He is dealing with a deficit because of the global financial crisis."

mfl