Magazine switches support to Cameron

Having backed Labour in 2005, an editorial in the latest edition said it was siding with David Cameron because the Tories were the party most committed to scaling back the size of the state.

"The Economist has no ancestral fealty to any party, but an enduring prejudice in favour of liberalism," the editorial said.

"But in this British election the overwhelming necessity of reforming the public sector stands out.

"It is not just that the budget deficit is a terrifying 11.6 per cent of GDP, a figure that makes tax rises and spending cuts inevitable. Government now accounts for over half the economy, rising to 70 per cent in Northern Ireland. For Britain to thrive, this liberty-destroying Leviathan has to be tackled."

Meanwhile, in a boost for Mr Brown, more than 100 economists put their names to a letter warning that Tory efficiency savings could lead to job losses and "destabilise" a fragile recovery.

The letter, signed by economists including Lord Layard, emeritus professor of economics at the London School of Economics, and David Blanchflower, a former member of the Bank of England's monetary policy committee, said the 6bn savings in 2010-11 amounted to a spending cut.

"It will lead directly to job losses and indirectly to further falls in spending through the standard multiplier process. At a time when recovery is delicate, it could even affect confidence to the degree that we are tipped back into recession - with much larger job consequences," it said.

"This is not the time for such a destabilising action. The recovery is still fragile."