Almost a quarter of private sector final salary pension schemes have been closed to all staff, a report found today.
The National Association of Pension Funds (NAPF) found that 23% of schemes have been shut to new staff as well as to future contributions from those already in the pension, an increase of nearly a third from 17% of schemes found to be closed a year ago.
The NAPF said employers were trying to manage risks and rising costs as final salary pensions have come under strain from increased longevity, poor investment results and red tape.
Joanne Segars, NAPF chief executive, said: "The private sector is seeing a seismic shift in its pensions, and more change is certain.
"Final salary deals are coming off the table and are either being watered-down or replaced altogether.
"Demographic and financial pressures mean businesses are struggling to afford these pensions. Many firms are trying to get a grip on the risks and rising costs by freezing the fund to both new and existing staff.
"While it is difficult to be exact, we estimate up to a quarter of a million have been moved out of their final salary pension over the past three years."
The survey, which covered around 1,500 schemes, found that more people will be "frozen out" in the near future.
Among those pension schemes which are closed to new staff but remain open to existing staff, just under a third are expected to close the scheme altogether in the next five years.
Around one in 10 (11%) of schemes plan to keep the existing defined-benefit pension structure, but will make it less generous, by moving from a final salary to a career average structure, for example.
Despite pressures on household budgets, contributions into pensions have remained broadly stable, the survey found.
Ms Segars said: "People will often find that the replacement pension on offer is a good one. It's encouraging to see that, despite the harsh economic climate, payments into defined contribution pensions by staff and their employers have remained stable.
"Whatever the type of pension, the main thing is to get more people saving. The UK simply isn't salting enough away for its old age."
Local government pension funds were also asked about people choosing to leave their pension, in the light of debate on public sector pension reform as well as squeezed household incomes. The report found that 39% said that opt-out rates had increased this year.
Figures released this week by the Pension Protection Fund (PPF) showed private sector final salary pension schemes are facing a record deficit of £222.1 billion.
The latest figure is the largest deficit since the records began in March 2003, but the PPF cautioned that direct comparisons are affected by changes made to its calculations from April.