The penalty charges amount to almost £14m as a result of the firms' failure to detect fraudulent customers. Daub Alderney has been fined £7.1m, Casumo has been fined £5.85m and Videoslots will pay £1m to a National Responsible Gambling Strategy project in lieu of a fine.

CZ Holdings decided to surrender its UK license after the review.

The Commission found Videoslots had failed to keep up with customer checks and monitor their activities. The operator accepted it had some flaws in its systems.

A spokesperson for Videoslots said: “We confirm that Videoslots has entered a regulatory settlement with the Gambling Commission to conclude a review of our operating licence. Their investigations were part of a thematic review by the regulator into AML and responsible gambling compliance in the remote gambling industry.

“We are pleased that the Gambling Commission recognises that we were open and transparent from the outset of their investigation and fully cooperative throughout.”

Neil McArthur, Gambling Commission CEO, said: “I hope today’s announcement will make all online casino operators sit up and pay attention, as our investigations found that a large number of operators and their senior management were not meeting their obligations.

“We expect operators to know their customers and to ask the right questions to make sure they meet their anti-money laundering and social responsibility obligations.”