The jump represents an increase of 17.1% compared with 2015 when the total was 33.5m. Active membership of occupational pension schemes was 13.5 million in 2016, split between the private (7.7 million) and public sector (5.7 million).

For private sector defined contribution schemes, the average total (member plus employer) contribution rate was 4.2% in 2016, broadly comparable with 2015. Membership of occupational pension schemes represents around 70% of all workplace pension membership, according to the ONS annual earnings survey data.

Fred Norris, spokesman for Economic Statistics at the ONS, said: "Today's figures show that total membership of Occupational Pension Schemes in 2016 is the highest recorded by ONS. Active membership continues to grow, predominantly in the private sector. In large part, this is likely attributed to the phased introduction of automatic enrolment."

Most experts have welcomed the news but again pointed out that average contributions to auto-enrolment schemes are too low.

Ian Browne, pensions expert at Old Mutual Wealth, said: “It is encouraging that auto-enrolment is gaining momentum, with occupational pension participation reaching record highs. But that is not the full story. Opt-out rates are low but not insignificant, and the real test will come in 2018 and 2019 when minimum contribution levels increase. They go up to 8% by 2019, and it will be important to keep an eye on participation rates then.

“There are also large numbers of people excluded, such as the self-employed, or those earning below the auto-enrolment threshold of £10,000. The earnings threshold is a particular issue for those working multiple jobs paying under £10,000, who are eligible for auto-enrolment based on total earnings  but don’t get pulled into the system because their income is spread between several part-time roles.”

Tom McPhail, head of policy, Hargreaves Lansdown, said: “More and more people are saving for retirement, which is great news but the data also shows how much work there is still to do. Average contribution rates will have to rise, and that isn't going to be popular; more work also needs to be done on making it easy for people to take control of their retirement savings.”

The average contribution rate to private sector defined benefit schemes is 22.7% of earnings while the average contribution rate to private DC schemes is 4.2%, HL points out.

• The figures come alongside news that the Pensions Regulator is beginning to take a tough line with non-compliance on auto-enrolment. This month the regulator launched its first prosecution of a company and its director for deliberately avoiding their automatic enrolment duties. Stott Tours, based in Oldham, Greater Manchester, and its managing director, Alan Stott, are accused of deliberately not putting 36 of their staff into a workplace pension. They have been summonsed to appear at Brighton Magistrates’ Court on 4 October.

Over 400,000 employers have now complied with their legal duties, says the regulator.