Statistics compiled by the Association of Consulting Actuaries shows that one in six pension schemes has been blocked to existing members.

Around 90% of the schemes that include final salary pensions are by now blocked to new members.

Another 18% of these schemes are blocked to further rise in pay-outs by the existing members.

ACA warned that the number of schemes that are closed altogether may rise in future.

About 40% of the 309 firms surveyed said they were mulling over altering the way benefits are accumulated, while 35% of the employers are considering switching over to a career average scheme. Under the career average scheme pensions are based on a worker's average pay throughout his career.

Twenty two per cent of the firms said they might opt for a defined contribution scheme, under which employees themselves face all the financial risks of investment plus increased life expectancy.

Almost 80% urged the Government to help them in offering 'middle-way pensions'.

At present, companies & employees contribute 29.5% of an employee's to defined benefit schemes as compared with 15.8% in 2002.