Professional services adviser Mercer has found that pension liabilities for FTSE 350 companies have increased by 44% since 2010, compared to 10% increase in market capitalisation.
It said defined benefit scheme deficits have grown by £34bn, although funding levels remain largely unchanged.
According to Mercer, despite some £15bn a year being paid into the defined benefit pension schemes of FTSE 350 companies, the deficits had increased before allowing for the impact of the referendum Brexit vote.
Mercer's analysis found these companies had a DB schemes total deficit of £64bn in 2010 corresponding to a funding level of 88%.
As of May 2016, the deficit was £98bn, although the funding level was almost unchanged at 87%.
Adrian Hartshorn, leader of Mercer's UK financial strategy group, said: "The high deficits are a result of the increase in the value of pension scheme assets not having kept pace with the rising cost of providing pension benefits caused by persistently low (and falling) interest rates.
"Contributions paid by companies are therefore simply being used to fill an ever increasing gap between the value of the assets and the value of the liabilities. Add to this the impact of people living longer and a range of other costs and it is easy to see how contributions are simply swallowed up."
Market capitalisation of the companies had risen by only 10%, even as their pension deficits ballooned by 44% and pension scheme liabilities now represent 40% of market capitalisation, compared with 30% at the end of 2010.
The outlook would become more positive only if interest rates rise more quickly than markets are expecting and equity markets perform strongly over a prolonged period while life expectancy improvements slow, Mercer said.
Hartshorn warned: "If one or more of these elements fails to materialize, then pension scheme deficits (and the cash contributions required to fund them) are likely to worsen.
"Pension schemes are an important part of a company's balance sheet and financing structure. Given the complex nature of pension scheme debt, companies often underestimate the positive impact that proactive intervention can have on managing the risk and cost of pension deficits."