In its annual survey, of 1,018 schemes run by 280 private sector firms, the NAPF found that only 13% were open to new joiners, down from 19% in 2011. And 31% were now closed to existing staff as well, up from 23% the previous year.
People living longer, red tape and poor investment returns as well as higher liabilities created by quantitative easing have prompted the fresh closures, according to the NAPF.
The NAPF said new staff in the private sector now had "next to no chance" of joining a final-salary scheme.
However, the survey does show that total contributions from both employers and employees into the newer type of 'defined contribution' pensions edged to an all-time high of 12.5% of salary in 2012, which is well above the 8% minimum that auto-enrolment requires.
Joanne Segars, NAPF chief executive, said: "The pressures on final salary pensions have proven too great for many businesses. The growing liabilities fuelled by quantitative easing will have been a factor behind the record hike in closures.
"Those starting a new job in the private sector have next to no chance of getting a final salary pension. What was once the norm is now a very rare offer. And those who are currently saving into one may find it gets closed."
Segars added: "We are in the midst of a pension regime change. Auto-enrolment will bring millions of workers into a new breed of pension that will come to dominate in the private sector. It is encouraging that savings into these pensions have reached a new high, despite the tough economic conditions.
"While many have closed their doors, private sector final salary pensions are far from finished. More than two million workers are still saving into one and they pay the pensions of over four million pensioners. It is essential that the Government shows them more support in managing some extremely testing economic circumstances."
