Public sector net borrowing rose to £15.4bn in December - £600m higher than in the same month in 2011.
The Office for National Statistics (ONS) data, which excludes financial interventions like bank bailouts, were slightly higher than the £15.2bn expected by economists.
The figures take total borrowing so far this financial year (excluding a one-off transfer of Royal Mail pension assets) to £106.5bn - £7.2bn higher than in the same period in 2011.
The tax and spending watchdog, the Office for Budget Responsibility (OBR), said it expects borrowing to hit £108.5bn in 2012/13, but some economists are unconvinced.
National Australia Bank's Tom Vosa said he was unsure how the Government planned to meet its borrowing requirement this year.
"The good news is that it suggests the public sector essentially has supported the economy in the fourth quarter and ahead of GDP data on Friday," he said.
"But overall, without further downward revision to borrowing data or a significant increase in income in January, it's difficult to see how the Government will meet its borrowing targets."
Martin Beck, economist at Capital Economics, added that the figures confirmed the Government's fiscal consolidation plans were still off track.
He expects borrowing for the financial year to come in above the OBR's forecast at £113bn.
However, a Treasury spokesman said the figures underlined that the recovery in the Government's finances was taking time but the economy was healing.
On Friday the ONS is expected to reveal that output contracted in the final quarter of 2012, which - combined with the borrowing figures - would put further pressure on the UK's AAA credit rating.
Currently, all three of the major credit ratings agencies now have the UK on negative outlook.
ING economist James Knightley said: "The question is how long the UK can hold on to its AAA status.
"With the US and France having been downgraded by one ratings agency in the past couple of years, another disappointing UK borrowing number and a widely expected contraction in GDP on Friday will intensify the threat of the UK suffering the same fate."
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