Chancellor Gordon Brown has announced a change in the way he will calculate the budget.

Brown cancelled next year's scheduled spending review, heralding a change in his famous "Golden Rule" that the government should not borrow over the economic cycle.

The economic cycle begun in 1999-2000 is due to end in 2006. Economists, however, have warned Brown will miss his economic targets and undoubtedly have to introduce large tax rises to sustain public finances and meet his golden rule.

Suggesting he hopes to avoid this path to pave the way for his premiership, Brown told the House of Commons Treasury select committee he now believes the current economic cycle started in 1997-98.

The move shifts the cycle back two years to when the government's budget was in surplus, giving Brown an extra £10 to £13 million in leeway.

Brown said the move was prompted by revisions from the Office for National Statistics (ONS) to economic growth and insisted he still would have met his financial targets next year.

"It is not at all clear why the [ONS] now believes that the economic cycle started in 1997, rather than 1999 as was previously held," said Ian McCafferty, chief economist with the Confederation of British Industry (CBI).

"The announcement only serves to highlight the sharp contrast between monetary policy, which is well-understood and appears genuinely free of political involvement, and fiscal policy, where the Treasury is able to act as both judge and jury."

McCafferty said the revision will do nothing to improve the chancellor's chances of meeting the rule in the next cycle.

George Buckley, of Deutsche Bank, questioned whether the move was justified.

"This certainly makes it more likely that the Golden Rule will be met over the cycle…but does little to address the recent deficits and thereby the ability of the government to meet its fiscal rules over the next cycle," he said.

The Treasury will now have the opportunity of setting spending levels for every government department through the first quarter of 2011, allowing Brown to meet his targets at a time when he is widely expected to take over as prime minister."