The number of whistleblowing reports sent to The Pensions Regulator has soared by almost a third.
A Freedom of Information request submitted by law firm Clyde & Co reveals TPR received 2,545 reports in 2015/16, up 29 per cent from 1,968 in 2014/15.
Last month new data showed the number of escalating penalty notices issued by the regulator had quadrupled.
It issued 96 escalating penalty notices to employers that failed to comply with auto-enrolment rules between January and March.
This compares to just 24 between October and December 2015.
Also in April, Swindon Town Football Club was fined £22,000 for repeated infringement of auto-enrolment rules.
The club was issued with a fine of £400 after it missed an initial deadline to begin enrolling staff, and was handed further fines of £2,500 a day for each day beyond a 28-day period that it failed to comply.
Clyde & Co head of pensions Mark Howard says: “The final stages of the auto-enrolment process are likely to be the most challenging, as there are so many employers that will need to enrol their employees.
“On top of this, the SMEs yet to face their enrolment deadlines are not going to have the support of HR departments to help them deal with the administrative headache of enrolling their employees into a pension scheme.
“TPR has put out a lot of guidance aimed at SMEs, but even so it is not surprising we are seeing the number of whistleblowing and enforcement actions increase as the number of employers subject to auto-enrolment grows substantially.”