The Tories are planning to repeat the 'Labour tax bombshell' campaign that won them the 1992 general election. David Cameron will argue Labour has £15billion of unexplained tax cuts, having voted to back Government plans to save £30billion over five years. Yesterday, the Prime Minister torpedoed Labour's central economic attack by categorically ruling out a rise in VAT. Asked by Ed Miliband at the final Prime Minister's Questions before polling day whether he would rule out a rise in VAT, he replied: 'The answer is yes.' The announcement left Mr Miliband, who appeared unprepared for the 'straight answer' he had demanded, floundering. Scroll down for video . Labour MPs sat stony-faced as Tory MPs roared with laughter when Mr Cameron ruled out a VAT increase . Labour had planned to make the possibility of a Tory VAT rise a key part of the election campaign. It has already drawn up billboards featuring a swinging block of concrete in the shape of the letters VAT. Mr Cameron then challenged Mr Miliband to rule out the prospect of Labour raising national insurance contributions, which it did in 2002. The Labour leader repeatedly declined to do so, saying the Tories would have 'plenty of time to ask questions' after polling day on May 7. However, within two hours of PMQs finishing, Shadow Chancellor Ed Balls issued a different message. 'We will make it clear in the manifesto Labour will not be raising national insurance. That will be a clear pledge from us,' Mr Balls said. Later he ruled out any increase in either the basic or higher rate of income tax. 'We have clear pledges. No rise in VAT under Labour, no rise in the basic and higher rates of income tax under Labour, no rise in national insurance under Labour,' Mr Balls said. 'Our plans add up, theirs don't. As night follows day, if people vote Tory VAT will go up. It always does and it will again.' Conservative sources suggested the party had set a trap for Mr Miliband because Chancellor George Osborne had repeatedly refused to rule out a rise in VAT under questioning from Labour MPs. 'Labour has been panicked today into ruling out tax rises left, right and centre,' said a senior official. 'So where is the £15billion tax bombshell going to fall? It is a safe bet that this is going to feature heavily in our campaign.' Conservative sources said the party had set a trap for Mr Miliband because Chancellor George Osborne two days ago (pictured) declined to give a 'cast-iron guarantee' to match Labour's pledge not to increase VAT . In an echo of slogans in the 1992 election campaign, when John Major defied the polls to win a majority, Mr Cameron said: 'We know there is a tax bombshell coming from Labour … It would wreck our economy.' The issue is likely to figure in the first leaders' TV interviews of the election campaign tonight, when Mr Cameron and Mr Miliband face a grilling from Jeremy Paxman and Kay Burley on Channel 4 and Sky News. The Tories have claimed they do not intend to raise any taxes, instead saving £13billion from the budgets of Government departments, £12billion from cutting the benefits bill and £5billion from measures to squeeze tax avoidance. However, they have to find £7billion to fund two tax pledges by the end of the next parliament – an increase in the personal allowance for income tax to £12,500 and the threshold for the 40p rate rising to £50,000. The announcements from the Conservatives and Labour severely restrict the room for manoeuvre of both on taxation after the next election because VAT and national insurance raise huge amounts for the Treasury. Raising significant sums elsewhere might require new taxes on businesses. Mr Miliband insisted 'nobody would believe' Mr Cameron's pledge and Labour officials said the party would press ahead with its billboard campaign. They pointed out that Mr Cameron had said before the last election that he had 'no plans' to raise VAT. Mr Osborne raised VAT from 17.5 to 20 per cent in his emergency budget in June 2010. Labour said the Tories had made a similar pledge before the 1992 election, only to break it a year later. Last night, Mr Cameron was cheered as he addressed the last meeting of the backbench 1922 committee of this parliament. 'We've got the song, we've got the tune, we've got the lines, we've got the policies,' the Prime Minister said. 'So let's get out there and sing about it. Let's get out there and win.'
The Tories are planning to repeat 'Labour tax bombshell' of 1992 election . David Cameron will argue Labour has £15billion of unexplained tax cuts . The Prime Minister torpeoded a Labour attack by ruling out VAT increase . Mr Cameron's straight answer left Mr Miliband floundering during the PMQs . Mr Cameron has had two detailed discussions about the prospect of another coalition – with senior Tories contemplating a three-way deal with the Liberal Democrats and Northern Ireland's DUP, it is claimed in today's Spectator magazine.