The Pensions Regulator issued 96 escalating penalty notices to employers that failed to comply with auto-enrolment rules between January and March, four times the amount in the previous quarter.
Between October and December 2015 TPR issued just 24 escalating penalty notices.
There have been 127 escalating penalty notices issued since auto-enrolment was introduced in April 2012.
A TPR spokeswoman says the rise relates to the rising number of employers using auto-enrolment, including more small businesses.
Between January and March TPR issued 806 fixed penalty notices – where a business is fined £400 – bringing the total issued since 2012 to 2,234.
TPR executive director for auto-enrolment Charles Counsell says: “It’s simply not fair for staff not to receive the pension contributions they are legally due.
“But failing to act also means an employer risks clocking up a significant penalty until they put things right.”
Pensions Minister Ros Altmann says: “The aim of automatic enrolment is to get all employers setting up pension schemes for their staff. It is most encouraging to see that even the smaller employers are managing to do this, and the proportion facing enforcement action has stayed remarkably low.”
More than 95% of the first small employers required to put their staff into a workplace pension have complied with the law.