In the past year, the combined pensions deficit of firms on the UK's FTSE 100 index has increased 13%, according to JLT Employee Benefits.
That could cause problems when some firms carry out pension re-valuations in the coming months, JLT said.
Tesco and Lloyds bank are among those re-valuing their pension schemes.
UK companies have to measure the deficit or surplus of their defined benefit pension schemes every three years.
"With many pension schemes now embarking on their triennial actuarial valuations and deficits likely to be much bigger than three years ago there are going to be some difficult discussions between companies and pension scheme trustees," said Charles Cowling, a director at JLT.
Companies could be forced to put much more money into their pension schemes to reduce the deficits, he said.
JLT found that the combined pension funds deficit of FTSE 100 companies was Â£60bn in April, up from Â£53bn a year ago.
The deficit of all UK private sector pension schemes was unchanged at Â£182bn, JLT found.
They "remain high due to quantitative easing and record low interest rates," Mr Cowling said.

The pop star owns Shafin Developments Limited with his brother Finbarr. It was involved in developments in Counties Leitrim and Sligo.
KPMG has been appointed as the receiver behalf of the Ulster Bank.
Westlife is one of the most successful boy bands of the last decade, selling more than 44m records.
In 2010, Westlife made the Irish Sunday Times musicians' rich list for the first time, with an estimated combined fortune of Â£31m.
The band, which also includes Mark Feehily, Kian Egan and Nicky Byrne, shared fifth place with singer Chris de Burgh.
The fifth member of the orginal line-up, Bryan McFadden, left Westlife in 2004 to embark on a solo career.
Last October, the band announced they would split up in 2012.
A final, farewell tour is due to start in Wales on 10 May.
On Thursday, KPMG confirmed that Patrick Horkan has been appointed as the receiver and manager to Mr Filan's company.
KPMG said Shafin Developments Limited's assets include four residential properties and a part developed site at the Hillcrest Development in Dromahair, Co Leitrim.
It added the firm also has "an interest in a site at Carraroe, County Sligo".
A spokeswoman said the move did not apply to Mr Filan's personal assets.
Shafin Developments Limited was established in 2004 and is registered in Mr Filan's home county of Sligo.
Some of the UK's biggest companies face "difficult discussions" over their growing pension deficits, according to a pensions consultancy.
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A property development company belonging to the Westlife singer Shane Filan has been placed in receivership in the Republic of Ireland.