Contributions to defined contribution (DC) pensions have increased by a fifth in the last year, data from the regulator has found.
According to The Pensions Regulator (TPR) £5.4bn was put into defined contribution (DC) pension schemes last year, an increase of more than 21 per cent year-on-year.
The regulator's annual DC Trust report showed that a total of £48bn is now saved in DC pension schemes.
Memberships have also increased.
At the end of the levy year 2016 to 2017 12.6 million people were members of DC pension schemes, up 29 per cent over the past year and up more than 400 per cent since the start of 2010.
Master trusts, which account for a major proportion of the increase, have seen membership numbers increase from 270,000 at the start of 2012 to almost 10 million in 2017.
By comparison, as of March 2017, there were 10.5 million members in defined benefit schemes with a total of £1,541bn assets, according to the Pension Protection Fund's Purple Book.
Anthony Raymond, acting executive director for regulatory policy, analysis and advice at The Pensions Regulator, said: "The success of automatic enrolment has put DC schemes – and particularly master trusts - at the heart of pension saving in the UK, and our figures illustrate this trend.
"For these new and existing savers we have a role to protect their benefits and so we are working hard to drive up standards of trusteeship."
About 90 per cent of people currently saving into a private sector pension are doing so into a DC scheme, the regulator said.
But as more people start saving into pension schemes for the first time, the average asset per membership declined from £4,700 in 2016 to £3,900 in 2017, the regulator added.
The Pensions Regulator is currently implementing the Pension Schemes Act 2017, which requires master trusts to become authorised and meet a clear set of standards in order to obtain authorisation.
Master trusts are a type of workplace pension scheme which have become increasingly popular since millions more workers were brought into the pension market as part of auto-enrolment.
Those not authorised by the The Pensions Regulator will be deregistered by HMRC under new powers given to the tax office in April.
The regulator also found the number of schemes in the market has continued to shrink.
Since 2010 the number of schemes, not including micro or self-administered schemes, has reduced by 52 per cent, from 4,560 to 2,180 schemes, according to the regulator.
Mr Raymond said: “We welcome the continued reduction in numbers of DC schemes. We have been concerned about a tail of sub-standard schemes and have been encouraging trustees who cannot or will not meet the standards we expect to consider consolidation."
The regulator's report is based on data provided by schemes on returns issued from July to December 2017 and related to the levy year 2016 to 2017 or earlier.
The scheme return is how the regulator collects information about occupational schemes.
Defined contribution schemes with 12 or more members complete a scheme return annually while schemes with two to 11 members complete once every three years.