UK pension deficits rose by £11bn yesterday, the highest single-day rise since FRS17 was introduced in June 2001.

The pensions deficits freefall was a caused by a drop in stock markets combined with a fall in bond yields, which saw pension schemes' liabilities rise by £5bn on the same day their assets fell by £6bn.

This news came just days after it seemed likely that February would see UK pension deficits fall to a four-year monthly low, following almost four months of positive financial market activity.

Despite the record rise, deficit levels have only increased back up to what they were in 30 November 2006 and are still almost half the level they were a year ago. At close of business on 27 February, the combined deficit for the 200 largest UK pension schemes was £45bn, with FTSE100 deficits standing at £35bn.

Marcus Hurd, senior consultant and actuary at Aon Consulting, said of the figures: 'Any sudden rise in deficits is unwelcome, but shocks such as this are to be expected. In the six years since FRS17 was introduced, there have been more than 20 individual days when the FTSE fell by more than yesterday, including two during 2006.