The aggregate funding position of the 7,400 defined benefit pension funds monitored by the Pension Protection Fund worsened to a deficit of £173.2bn in August.
The deficit stood at £158.1bn at the end of July.
Scheme funding is worse than it was a year ago when there was a deficit of £39.3bn in August 2008.
The total deficit of schemes in deficit in August is estimated to have worsened to £194.6bn from £179bn at the end of July.
In August last year, the aggregate deficit of all schemes in deficit stood at £92.7bn.
In August this year, the total surpluses of schemes in surplus increased to £21.4bn from £20.9bn at the end of July 2009. Last month, the total surplus of all schemes in surplus stood at £53.4bn.
The number of schemes in deficit in August this year stood at 6304 - up from 6265 schemes in deficit in July.
The PPF says this represented 85% of the total number of DB schemes in the sample.
It blames falling equity markets and bond yields for the "overall worsening of the funding position".
It says lower bond yields resulted in a 9.6% increase in aggregate liabilities while weaker equity prices reduced assets by 3.1% over the year.
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