Millions of employees due to be enrolled in workplace pension schemes for the first time are becoming less willing to put money into them despite concerns about a shortfall in contributions, figures show.
A report from Scottish Widows finds those facing auto-enrolment under a landmark Government scheme are prepared to save just £51 each month towards retirement savings, a fall of 24% compared to last year when the figure was £67.
Yet even those within existing "defined contribution" schemes - who contribute a larger amount - are facing a large gap between their expectations of income in later years and the reality of what their pension pots are likely to buy them.
Experts said it highlighted the need for better explanation of pension schemes to help employees make the "hard choices" needed.
The research showed those earning £10,000-£30,000 are on average likely to receive only about half their desired annual income. Average contributions of £85 are expected to produce yearly pensions of £11,700, compared to a hoped-for £22,800.
It represents a monthly retirement shortfall of £658 for those in that wage bracket. The average gap is £669 - when including those on higher pay who have higher expectations for post-retirement income.
The report said: "This shortfall between current savings and desired annual income in retirement indicates that despite the positive impact of auto-enrolment, employees are still removed from the reality of retirement."
A shake-up in pensions starting last year means that millions are being automatically enrolled in schemes that would see them contribute a minimum of just 0.8% of earnings, or £2.37 a week for someone on a £20,000 salary.
Minimum contributions, which are topped up by employees and through tax relief, will later increase. Workers can opt out but if they do so will miss out on employer top-ups.
Auto-enrolment was introduced to tackle growing concerns about an old-age poverty crisis as people live for longer but fail to put away enough money for later years.
More than one million people have been enrolled in a workplace scheme since it was launched but the Scottish Widows Workplace Pensions Report found that the 8.6 million still be auto-enrolled were increasingly less willing to contribute.
While the £51 they were prepared to invest on average was still above the minimum requirement for the scheme, it fell well below what was needed to match retirement aspirations, the report said.
It also found that while awareness of auto-enrolment among workers was increasing, many still did not know how much they or their employers were contributing.
Lynn Graves, head of business development for corporate pensions at Scottish Widows, said: "We cannot ignore the fundamental correlation between poor employee awareness of the scheme and the lack of understanding of the realities of retirement.
"The alarming fall in the amount that employees are willing to contribute only serves to highlight this."
Tom McPhail, head of pensions research at Hargreaves Lansdown, said auto-enrolment was fixing part of the pensions problem, with participation rates increasing rapidly and opt-outs remaining low, but the report showed there was far to go.
"Most employees aren't saving enough as it is, yet according to this research the amounts they are willing to save are actually falling.
"This highlights the vital role that employers, advisers and pension companies have to perform in helping employees to plan effectively for retirement.
"Saving adequately for retirement is never going to be something that the majority of employees will actively choose to do because it involves making hard choices.
"So you have to show them how to do it, explain how it works, put them in control, simplify the paperwork and make it easy for them to make the hard decisions."
Pensions Minister Steve Webb said: "We are helping people to plan for their retirement through automatic enrolment, and despite the difficult economic times, take-up has radically outstripped expectations.
"In less than a year, we have seen 1.4 million people join a workplace pension scheme. This shows that when we make things easy for people they will engage with pension saving."