Britain's plan to cut deficit inadequate, says Brussels

Double blow for Brown as polls suggest Conservatives' lead is growing

Britain is to be told to take tougher action to cut the country's debt mountain in an embarrassing rebuke from the European Commission.

The wounding verdict on the Government's economic strategy – described by Brussels as unambitious – came as two opinion polls suggested that Labour's success in eroding the Conservative lead had faltered.

The Commission raised doubts over whether Britain would hit a European Union target to cut the national deficit below 3 per cent by 2014-15. Its finding is a warning of the scale of spending cuts and tax rises that the winners of the election will have to make to reduce Britain's debts over the next four years.

"The overall conclusion is that the fiscal strategy in the convergence programme is not sufficiently ambitious and needs to be significantly reinforced," said a leaked draft of the Commission document obtained by Reuters. "A credible time-frame for restoring public finances to a sustainable position requires additional fiscal tightening measures beyond those currently planned."

Britain's plan envisages cutting the gap from the predicted 12.1 per cent of gross domestic product in 2010-11 to 4.7 per cent in 2014-15. But the document, expected to be approved by the Commission tomorrow, warns that Britain may not even hit its own target because economic growth could turn out to be lower than the Government forecasts.

George Osborne, the shadow Chancellor, described the assessment as "a heavy blow for Gordon Brown's credibility". He said: "The Conservatives have been arguing we need to reduce our record budget deficit more quickly in order to support the recovery. Our argument is backed by credit rating agencies, business leaders, international investors and now the European Commission."

A Treasury spokesman said Alistair Darling, the Chancellor, had taken a "judgement on the appropriate pace of adjustment in 2010-11 and beyond".

He said it took into account "the uncertainty around prospects for the public finances, given the exceptional nature and strength of the global downturn, the need to support the economy through the early stages of the recovery and the need to deliver sustainable public finances".

Today's polls found that the Tories had increased their lead over Labour, reversing the trend over the last two months. The ICM poll for The Guardian put the Tories on 40 per cent (up three points since last month), with Labour on 31 per cent (up one) and the Liberal Democrats unchanged on 20 per cent. The Conservative lead of nine points would put the party just six seats short of an overall majority.

The Opinium survey for the Daily Express also showed the Conservatives widening their advantage, suggesting that the party could win an overall majority of 40 seats. It put the Tories on 39 per cent, up two points on last week, and 11 ahead of Labour, who were down two on 28 per cent. The Liberal Democrats were unchanged on 16 per cent.

Recent surveys had pointed to a hung parliament after the election expected on 6 May, with the Liberal Democrats holding the balance of power and Labour possibly the biggest party.

Last night, in his first election rally, David Cameron urged Tory activists in London to campaign on a commitment to "change, change, change" the economy, society and politics.

Earlier, Mr Brown hinted that he would try to remain as Labour leader even if he is defeated at the election. Asked on BBC Radio 4's Woman's Hour whether he would resign if he did not get a majority, he replied: "I'll keep going."