The collective deficit of the UK's final salary pension funds grew by over £12bn in August.

According to figures released by the Pension Protection Fund, the total deficit now stands at £36.7bn, up from £24.1bn. In July 2007 there was a surplus of £59.1bn.

The overall assets of the pension schemes actually rose in August, the PPF revealed, but the value of their liabilities increased by an even greater amount.

"During the month of August 2008 there was a 3.5% increase in assets due to rising UK and global equities," said the PPF. "Meanwhile, lower gilt yields led to a rise in liabilities of approximately 5%."

Only 23% of schemes now remain in surplus, the PPF added.