Senior Conservative MPs will attack Labour's general election promises by accusing Ed Miliband of pledging £20.7bn of unfunded commitments.

The cabinet ministers, led by the Chancellor George Osborne, will claim that Labour's first year in office alone will total billions of pounds.

Osborne, Theresa May, William Hague, Nicky Morgan and Sajid Javid will unveil the analysis of Miliband's plans.

"When we took office four and a half years ago, we were left a note by the Labour Party saying simply: 'there's no money left'," a Conservative spokesman said.

"The mess we were left behind by Labour threatened this country's economic security and the economic security of everyone living here.

"But the evidence we will produce shows that Labour have not demonstrated the fiscal discipline or economic competence that earns an opposition the credibility to form a government.

"The chaos of unfunded spending promises, higher taxes and more borrowing offered by Labour is a risk to economic recovery. Competence or chaos. That is the choice for the British people at the election."

But Labour have hit back at the attack and promised that the party has made no unfunded commitments.

"It is David Cameron and Osborne who have made more than £7bn ($10.7bn, €8.9bn) of unfunded tax promises," said Chris Leslie, shadow chief secretary to the Treasury.

"These could only be paid for by another Tory VAT rise, even deeper cuts to public services or both.

"Labour has made no unfunded commitments. In fact the Institute for Fiscal Studies said last month that we had the most cautious approach and, unlike the other parties, had promised no net giveaways.

"If the Tories wanted a serious debate they would not be blocking our proposal to allow the OBR to independently audit the manifestos of the main parties. Instead it's clear they want to carry on spreading smears about Labour while avoiding scrutiny of their own plans.

"It is George Osborne's plan to slash public spending back to a share of national income last seen in the 1930s which is the real risk to Britain's future."

Miliband, launching Labour's "long election campaign", is expected to promise that the party will speak directly to four million voters ahead of the 2015 General Election in May.