The Gambling Commission said it had carried out more than 160 investigations from 2018 to 2019 and betting companies have paid out £19.6m in penalties.
The commission imposed a variety of sanctions on operators to include fines for failing to protect problem gamblers and prevent money launderers.
Online casino company Daub Alderney was ordered to pay £7.1m and Paddy Power Betfair was fined £2.2m.
Gambling Commission chief executive Neil McArthur said, ““I want gambling consumers in Britain to be able to enjoy the fairest and safest gambling in the world and I want gambling operators to work with us to put customer enjoyment and safety at the top of their corporate agenda.
“As the report shows, we will be tough when we find operators bending the rules or failing to meet our expectations, but we also want to try and minimise the need for such action by providing advice, a programme of support material and compliance activity to help operators get things right in the first place.”
The Gambling Commission’s report said that a “substantial number” of investigations were carried out in the online gambling sector.
The probe found that anti-money laundering policies were not fit for purpose.