Borrowing rose from £14.46bn in August 2011, the Office for National Statistics said today, marking the highest August since records began in 1993.
A fall in corporation tax receipts and a rise in benefit payments were behind the jump.
It took borrowing in the fiscal year to date to £31bn, down from £48.44bn in the April-August period 2011.
The government had originally planned to eliminate the structural budget deficit by 2015 with a tough programme of spending cuts and tax rises.
Howard Archer, chief UK and European economist at IHS Global Insight, said today: "It is likely in the Chancellor's autumn statement that he will either have to acknowledge that he will be unable to start bringing down debt as a percentage of GDP by 2015/16 or announce further fiscal tightening measures."