Less than half of employees in the UK have enrolled into a workplace pension scheme, according to new research.

The Office for National Statistics (ONS) has published new figures which show that just 48 per cent of workers were saving into an employer's scheme in 2011.

This figure represents the lowest proportion since the ONS first began recording enrolment data in 1997, when 55 per cent of British workers were in a scheme.

Public sector staff were much more likely to be in a workplace pension, with 83 per cent of employees saving into a scheme, compared with just 33 per cent of those in the private sector.

Darren Philp, policy director at the National Association of Pension Funds (NAPF), expressed his concern at the falling number of private sector workers enrolling into pension schemes.

He said: "While reform is coming to the public sector, the private sector has already seen a seismic shift in its pensions. Over the past decade, many final salary deals have come off the table to be replaced with newer 'money purchase' pensions.

"Sadly, the fall in people saving into a final salary scheme has not been fully matched by interest in other types of pension."

According to the ONS study, private sector membership of final salary schemes - in which payouts are pre-determined dependent on salary and duration of employment - fell from 46 per cent in 1997 to 30 per cent in 2011. Meanwhile, just under eight in ten (79 per cent) public sector workers were part of final salary schemes.

Mr Philp claimed that the figures could be improved by auto-enrolment, with the reforms expected to bring "between five and nine million people into a pension", including younger people and many part-time workers.

The ONS figures are based on the findings of its Annual Survey of Hours and Earnings, which looked at a small sample of all employee PAYE tax records.