The Liberal Democrats have accused the Conservatives of planning a "VAT bombshell" costing every family £389 a year to pay for tax "bribes".

Mr Clegg said the Tories would be forced to raise VAT to 20.5 per cent to pay for £13.5 billion in tax breaks pledged by Mr Cameron.

He acknowledged that the wealthy would be hit by higher taxes under his own plans to raise the income tax threshold to £10,000.

Speaking in Glasgow at the launch of his party's Scottish campaign, Mr Clegg said only the Lib Dems would be able to cut taxes for middle and low income people.

He said: "The Conservatives have made a series of uncosted tax promises - tax bribes. The only way that they are going to deliver their tax promises is by dropping a tax bombshell, a VAT bombshell of £389 a year on every household in this country."

The Conservatives have pledged to recognise marriage in the tax system, limit the National Insurance rise, freeze council tax and raise the inheritance tax threshold.