Public sector net borrowing hit £14.5bn in June, marginally below the shortfall of £14.7bn one year earlier but still worse than economists had expected.
Figures from the Office for National Statistics (ONS) show a Budget deficit of £13.3bn, with net debt at the end of June standing at £926.9bn, or 63.9% of GDP.
The data pours water on the idea the UK's public finances are on an improving trend, says Jonathan Loynes, the chief European economist at Capital Economics.
"Along with an upward revision to May's deficit, June's borrowing total of £14.5bn left a cumulative deficit in the first three months of the year of £40.3bn, only a fraction below the £40.9bn figure recorded in the same three months of last year," he says.
"Extrapolating this forward points to a full-year deficit of about £152bn (on the PSNB ex. measure), about £3bn above the Office for Budget Responsibility's Budget forecast.
"Admittedly, this would be a very small overshoot compared to those seen in recent years. Nonetheless, it does perhaps dampen hopes that the public finances might improve more quickly than the OBR has predicted over the coming months."
However, IHS Global Insight's chief UK and European economist Howard Archer says it is important not to read too much into data over just one month. He expects Chancellor George Osborne to be able to meet his public sector borrowing target of £149bn in 2010/11 despite these disappointing numbers.
Sterling fell to a session low against the euro in response to the data, tumbling to 1.1724. It also fell 0.4% against the US dollar, to $1.5219.
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