The government borrowed £1.4 billion more in August than it did a year earlier, according to the Office for National Statistics (ONS).
£12.1bn was borrowed in August, compared with £10.7bn in August 2014.
However, public sector borrowing is down £4.4bn in the year-to-date compared with the same period last year. After four months of the financial year, the UK government has borrowed £38.4bn, down from £42.8bn last year.
The ONS said that given volatility in borrowing, cumulative year-to-date figures are much more representative of the overall picture that monthly figures.
Public sector debt now stands at £1.505 trillion, which represents 80.6% of the UK's GDP, after a £68.9bn rise on August last year.