Economists were unsure if the poor reading was a one-off or the start of a new downturn for public finances in Britain, where the budget deficit totaled 10.4 percent of gross domestic product (GDP) last year, one of the highest among major economies.

But either way Tuesday's official data give the government a poor starting point from which to begin the toughest spending cuts in a generation next year, as it seeks to almost eliminate the deficit by 2015.

The Office for National Statistics said public sector net borrowing rose to a record 22.8 billion pounds from 16.7 billion pounds last November, pushed up by a big rise in spending on defense, health and the European Union, and slow revenue growth.

Economists had forecast a deficit of just 17 billion pounds, and November's overshoot wipes out almost all the savings made since the fiscal year started in April - causing sterling to fall to a three-month low against the dollar.

The government forecasts that PSNB excluding financial sector interventions will fall to 148.5 billion pounds in the 2010/11 fiscal year from 156.3 billion pounds last year, and said Tuesday's data did not change this.

However, economists pointed out that total PSNB-ex between April and November of 104.4 billion pounds was now just a billion pounds lower than in the 2009/10 tax year, compared with a cumulative saving of around 6 billion pounds last month.

"This is dire news for Chancellor George Osborne to digest over Christmas," said IHS Global Insight economist Howard Archer. "There is now a very serious risk that the government will miss its fiscal targets for 2010/11. Much will depend on how well growth holds up over the rest of the fiscal year."

Investec economist Philip Shaw said that extrapolating the current trend, PSNB-ex would total 155 billion pounds this year, rather than the 148.5 billion pounds or 10.0 percent of GDP forecast by the government's Office of Budget Responsibility.

"The figures are extremely disappointing and a bit of a bolt out of the blue," Shaw said. "It is very difficult to judge whether this is just a rogue figure or whether it represents something more fundamental."

The ONS said the deterioration was due to a 10.8 percent rise in central government spending compared with a year ago combined with an annual rise of just 3.1 percent in tax revenues - the smallest since last December.

Local government borrowing last month was more than treble that of a year ago at 2.9 billion pounds, although the ONS said this was a volatile measure and could possibly be revised lower in subsequent months.

The ONS said public sector net debt including financial sector interventions rose to 65.2 percent of GDP, its highest since records began in March 1993. Excluding financial sector interventions, public sector net debt was 58.0 percent of GDP.

"These outturns are in line with the OBR's latest forecast for borrowing to fall by almost 10 billion pounds this year compared to last," said a Treasury spokesman.

However, the government may face an uphill struggle to meet its spending targets over the rest of the year. Unemployment unexpectedly rose for the first time in six months in the three months to October, and unusually cold and snowy weather in December may depress fourth-quarter output and tax revenue.

Public concerns about the scale of austerity measures needed to reduce government borrowing - including a rise in VAT from next year - are already weighing on confidence. A survey by GfK NOP showed consumer morale at its lowest level since July in December.

"While the higher VAT rate from January should help to boost revenues, a sharp slowdown in consumer spending will dampen its near-term effect," said Hetal Mehta, economist at Daiwa Capital Markets.