In its annual auto-enrolment evaluation report, the government found while in 2012 the amount saved per eligible private sector staff member was £6,370 this had dropped to £4,673 in 2014.
The document suggested this is likely to be a result of the increased number of savers with the majority making contributions at the current required minimum levels.
In the public sector meanwhile, the rate of saving per eligible saver increased from 2012.
In 2014, the annual total amount saved in workplace pensions was £80.3bn, an increase of £2.7bn from 2013, but this was driven by the private sector, where saving increased by £3.1bn to £42.9bn, whereas in the public sector this fell slightly by £500m to £37.4bn.
Nathan Long, head of corporate pension research at Hargreaves Lansdown, commented that while the amount saved has dipped, this will self-correct when the legislation is fully rolled out and minimum contribution levels hit 8 per cent in 2018.
The largest increase in participation was by 18 per cent from the group earning between £10,000 and £20,000 and the in terms of age was 19 per cent amongst those aged 22 to 29 - up to 60 per cent in 2014.
Up to the end of September this year, more than 5.47m workers have been automatically enrolled by over 60,000 employers.
Of that, 10 per cent of automatically enrolled workers have opted out, with a further 3 per cent of automatically enrolled workers having ceased active membership after their month long window to opt-out finished.
The report also found both awareness and understanding of auto-enrolment between small and micro employers is on the increase, while the median cost of implementing the legislation for those firms was £500 - for those having commenced up to August 2015.
Mr Long noted even if just 1 per cent of the companies yet to stage do not comply, this is still almost 20,000 employers facing a problem.
“Too many people, such as the low paid, part-timers and the self-employed are still being left behind; we are looking to the government to address these outstanding issues of eligibility as soon as possible.
“It is notable that the government continues to pay no attention to the levels of opt-in, in spite of the fact that over 5 million employees working for companies that have already gone through auto-enrolment are still not members of a pension,” he added.
Earlier this month, The Pensions Regulator stated that it had closed almost 500 auto-enrolment cases and issued compliance notices to another 470 employers between July and September.
It also issued 469 compliance notices for contravention of one or more enrolment employer duty provisions, making a total of 2,248 to date.
The number of employers who received a fixed penalty notice was 107, while two employers received an escalating penalty notice for failure to comply with a statutory notice. The penalty ranged from £50 to £10,000.
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