Bookmaker William Hill has been fined STG6.2 million ($A12.2 million) for "systemic social responsibility and money laundering failures".
Britiain's Gambling Commission said an investigation had revealed that between November 2014 and August 2016, William Hill Group (WHG) breached anti-money laundering and social responsibility regulations.
Lack of proper checks resulted in 10 customers being allowed to deposit large sums of money linked to criminal offences, which resulted in gains for WHG of around STG1.2 million.
Commission executive director Neil McArthur said: "We will use the full range of our enforcement powers to make gambling fairer and safer.
"This was a systemic failing at William Hill which went on for nearly two years and today's penalty package - which could exceed STG6.2 million - reflects the seriousness of the breaches.
"Gambling businesses have a responsibility to ensure that they keep crime out of gambling and tackle problem gambling - and as part of that they must be constantly curious about where the money they are taking is coming from."
The body said some of the issues it found included the bookie not adequately seeking information about the source of punters' funds or establishing whether they were problem gamblers.
Examples of failures included one customer being allowed to deposit STG654,000 over nine months without any checks being carried out.
The Gambling Commission said the customer lived in rented accommodation and was employed within the accounts department of a business - earning around STG30,000 a year.
Another case saw one person allowed to deposit STG541,000 over 14 months, after an assumption based on a verbal conversation was made that their potential income could top STG365,000 a year, and no further probing undertaken.
In reality, the Gambling Commission said this person was earning STG30,000 a year and was stealing from their employer to fund their gambling habit.
Australian Associated Press
