The spot checks start later this month and will also target employers who are still non-compliant despite penalty action.
The inspections will include Essex, Kent, Hertfordshire, Bedfordshire and Cambridgeshire.
It followed spot checks already carried out in the North East, Northern Ireland, South Wales, Edinburgh, Glasgow, Greater Manchester, Sheffield and Birmingham.
Businesses can be fined tens of thousands of pounds if they are found to have given false information to the TPR.
The inspections are to detect non-compliance and also to gain insight into employer behaviour.
Any employer who has a member of staff aged between 22 up to state pension age and who earns at least £10,000 a year or more than £192 a week, must provide a pension scheme for the employee.
TPR’s director of automatic enrolment, Darren Ryder, said: “It is an offence for employers to provide TPR with false information on their declaration of compliance, but there are tell-tale signs indicating an employer might not be telling the truth.
“We can also detect employers who are failing to meet their automatic enrolment duties despite being issued with a penalty and we will take action if we suspect either of these is the case.
“The vast majority of employers are meeting their responsibilities and automatic enrolment is now business as usual.
“But where employers fail to comply with the law, we will use our full range of our powers to ensure staff get the pensions they are due.”
The Pensions Regulator website provides more information on employer pension duties.