More than 80% of defined benefit, or final salary pension schemes, are closed to new entrants, according to research by the Association of Consulting Actuaries (ACA).
This figure was up from 68% two years ago.
The number of schemes also closed to future accruals from existing members is 14%, up from 10% two years ago.
The survey collected responses from 336 employers with scheme assets exceeding £127bn and more than 2.1 million members.
The research also found a pattern of mounting pension costs for those employers running defined benefit schemes. Over the past five years, the average employer contribution has nearly doubled from 11.5% to 22.6% of earnings.
Member contributions too have increased, on average from 4.3% of earnings to 6.1%.
Association of Consulting Actuaries chairman Ian Farr said: “The big downside of the scheme closures that have taken place as private sector employers have de-risked for the future is that we are facing the very real prospect of growing ‘under pensioning’ in respect of millions, particularly the young and middle aged.
“The government must act quickly to encourage pension provision that is better than a minimum level through personal accounts, where we feel there is some over-optimism in terms of the scale and the reliability of the pensions that this scheme will deliver.”