Labour has launched a fresh attack on Tory tax and spending plans.

A costed Treasury document released to the Guardian newspaper on Monday claimed the Conservatives have £15.7bn of spending commitments unaccounted for.

The Tories hit back however, accusing chancellor Gordon Brown of "taking the election into the gutter with outrageous smears".

Brown is behind what Labour sources are describing as a "demolition" strategy, designed to undermine public confidence in Conservative plans to cut taxes by £4bn and repay £9bn of the national debt by reducing government bureaucracy, without hitting frontline services.

At a joint press conference with the chancellor, Tony Blair said: "The simple point is that you cannot, as a matter of economics, spend more, tax less and borrow less - all at the same time.

"How do you square this economic circle? It's economic nonsense."

The Tories have "uncosted spending commitments" they could not possibly fulfil, he said.

"When they say 40,000 extra police officers... where does it come from?

"It's an absolutely fraudulent prospectus unless they say this is where the money comes from."

James review

Labour is also planning to dedicate a day of its general election campaign to attacking the James review of government efficiency savings, on which the Conservatives have based their plans.

Ministers believe the Tory troubleshooter's report is flawed, and will hit the Opposition's poll hopes if subjected to serious scrutiny.

Shadow chancellor Oliver Letwin's tax plans do not take into account frontbench commitments to pay for 40,000 extra police officers, private healthcare and education vouchers, and the abolition of student fees, according to the Labour analysis.

Brown said: "Nothing in Letwin economics adds up. They claim to be able to spend more, tax less and borrow less, exactly what John Major promised in 1992."

"Taking £2bn out of the money earmarked for our local schools transferred into private schools for the few, withdrawing the equivalent of £200 per pupil from local schools, is a privatisation policy for a few that hurts every hard-working family in the country," he added.

Rebuttal

Letwin moved swiftly to rebut Labour's claims.

"These are truly desperate smears," he said. "Some of the allegations relate to spending commitments which we have made and are fully costed and funded within our published spending plans.

"Others are quite simply untrue. The figures they have produced are a complete mess.

"Four months ago they said our expansion of residential drug rehabilitation places would cost £220m. Now they have increased that figure to more than £1.2bn.

"These are false claims by a party that specialises in dodgy facts. It shows just how rattled Mr Blair has become."