The Gambling Commission is to lay down tougher rules for the industry in Great Britain after becoming exasperated by the ongoing failure of online casinos and bookmakers to protect vulnerable people and addicts.

In a major shift in emphasis, the regulator will start giving operators direct instructions on how to ensure that consumers aren’t harmed, taking a prescriptive approach, instead of leaving it up to them to decide how to do so.

The Gambling Commission chief executive, Andrew Rhodes, said the regulator had been forced to act because firms were “not doing enough”, despite the imminent threat of a government review of gambling laws that could lead to stricter regulation.

William Hill recently revealed that it had set aside £15m to cover potential costs arising from a review of its licence by the Gambling Commission.

If the regulator were to fine the bookmaker that much, it would be the highest penalty ever levied against a British operator.

Online casino 888, which is in the process of buying William Hill, was fined £9.4m last month over multiple failings that led to customers racking up huge losses during the depths of the Covid pandemic.

Rhodes said the regulator’s more prescriptive approach would leave firms in no doubt about what they need to do to avoid facing more penalties, the volume of which has risen significantly in recent years.

“Time and time again our enforcement cases show that some operators are still not doing enough to prevent gambling harm,” said Rhodes.

“These new rules, developed following an extensive consultation, make our expectations even more explicit.”

“We expect operators to identify and tackle gambling harms with fast, proportionate and effective action and we will not hesitate to take tough action on operators who fail to do so.”

Under the new rules, bookies and online casinos will be required to monitor a specific range of indicators that a customer is suffering harm due to their gambling, flag worrying signs and take action quickly.

They will also have to put in place measures to stop themselves marketing bonus offers for customers deemed to be at risk of gambling disorder.

The Gambling Commission will expect them to provide regular evidence of their progress. It plans to issue guidance on how to comply in June, before the rules come into effect on 12 September.

The Guardian has approached the Betting and Gaming Council (BGC), the lobby group for the industry, for comment.