Occupational and salary-related pension schemes have been wrong-footed by rising life expectancies, it has been claimed.
According to the Pensions Advisory Service (TPAS), the schemes were set up with definite mortality rates and costs in mind.
This means that costs have risen substantially as life expectancies have increased, according to spokesperson Des Hamilton.
"In recent years the institute has woken up to the fact that people are living longer and that's fed through into the cost of these schemes," he said.
He added that other problems have occurred through a number of separate factors, such as stock market fluctuations catching "a lot of pension schemes out".
Schemes got into deficit, Mr Hamilton explains, because the falling value of stock assets coincided with a rise in costs.
According to the Times, a quarter of large companies are debating whether to sell their pension schemes.
Find out more about occupational pensions
© Adfero Ltd