Annual government borrowing almost doubled as a share of GDP over the past year and is five times higher than before the financial crisis.

The data prompted sharp criticism by the opposition Conservatives and came hours ahead of a key televised debate between Prime Minister Gordon Brown and the leaders of the two main opposition parties, part of a closely fought run-up to a May 6 election.

All Britain's main political parties are agreed on the need to cut the deficit but the Conservatives say they would start this year while Labour and the third main party, the Liberal Democrats, want to wait until next year, saying to act now would imperil a fragile economic recovery.

The Office for National Statistics said the government's preferred measure of public sector net borrowing hit 163.4 billion pounds ($252.5 billion) in the fiscal year that ended in March, the highest since modern records began in 1946/47.

The Labour government, trailing in opinion polls, had forecast in its March budget that full-year borrowing would reach 166.5 billion pounds, a downward revision from December's estimate of 178 billion.

Sterling strengthened marginally versus the euro and dollar after the data, and the Debt Management Office trimmed issuance plans for the current fiscal year by 2.1 billion pounds to 185.2 billion pounds.

"The fact that the public finances were modestly less awful than feared in March and overall in fiscal 2009/10 does not materially alter the fact that they are in an almighty mess," said Howard Archer, chief UK economist at IHS Global Insight.

"Whoever is in power after the election will have to announce further major spending cuts and tax hikes to return the public finances to a sustainable state over the medium term."

The Conservatives said the data highlighted the parlous state of the economy.

"These borrowing figures remind us once again of the huge debt that has been built up under Gordon Brown. This year Britain will pay almost 42 billion pounds on debt interest alone - more than on educating our children," said Conservative lawmaker and finance spokesman Philip Hammond.

Brown will only get some comfort from the fact that full-year borrowing is slightly less than the government forecast, and that March tax receipts are up on a year ago.

"The government's action to help families and firms has supported the economy, and meant that tax receipts have come in better than many expected. Withdrawing support now would threaten the recovery - pushing borrowing higher not lower," said Labour's chief secretary to the Treasury, Liam Byrne.

Investors are worried that current opinion polls suggest no party will get an overall parliamentary majority - an unusual situation for Britain which could stymie agreement on how the budget deficit should be cut.

As a share of GDP, PSNB rose to its highest since records started in 1954/55, hitting 11.6 percent in 2009/10. This is up from 2.4 percent in 2007/08 before the financial crisis started, the fastest rise in borrowing of any major economy.

March's borrowing took total public sector net debt, including interventions to prop up Britain's financial sector, up to 890 billion pounds or 62 percent of GDP, the highest for a financial year since records began in 1974/75.

"This is still the biggest budget deficit since the World War II and on a rough par with that of Greece," said Jonathan Loynes at Capital Economics.

The measure of government borrowing that most closely represents the amount of new financing Britain needs, the public sector net cash requirement, showed borrowing of 25.8 billion pounds in March, well below economists' forecasts of 32 billion.

For the 2009/10 fiscal year, the PSNCR totaled 134.3 billion pounds, up from 59.6 billion in the 2008/09 fiscal year and the highest since records began in 1963/64.