The total shortfall in FTSE 350 companies defined benefit pension schemes has decreased by £7bn.
Consultancy Mercer said the deficit fell from £85bn at the end of August to £78bn on 30 September. The decline was driven by a fall in expected inflation, which reduced liabilities and offset the fall in equity markets over the month.
Based on data from Mercer's latest Pensions Risk Survey, assets were valued at £624bn at 30 September, a drop of £2bn from the previous month. However, liability values were £702bn, which represented a fall of £9bn from £711bn.
Ali Tayyebi, senior partner at Mercer's retirement business, said: "It might come as some relief that accounting deficits have improved further during September despite the continued fall in equity markets. However, recent events have highlighted the large number of complex interlinked global and UK-specific variables which will continue to drive the health of UK pension schemes going forward."
Tayyebi also said sponsors and trustees should consider the implications of the recent trend in mortality.
"The Continuous Mortality Investigation has also just published its latest annual update of mortality trends, which this time suggests a small reduction in projected life expectancy," he said.
"This is another area which sponsors and trustees must keep under review going forward and sponsors will particularly want to make sure this is considered for their next year-end disclosure."