Many smaller employers currently operating final salary pension schemes are likely to shut them down and rely on the government's proposed national pension plan, the Association of Consulting Actuaries has warned.

The new scheme will entitle any employee who is not already a member of a company pension scheme to join the government plan, which will eventually require employers to contribute 4% of an employee's salary, with the employee adding 3% and the government putting in a further 1% in tax relief.

But the ACA suggests 36% of companies with fewer than 250 staff will use the changes as a reason to close their own schemes, meaning many on final salary plans would be worse off in retirement.

The government's pensions bill is due for its second reading in January and the new regime is scheduled to come into force in 2012.