The Gambling Commission is investigating claims that the online casino company LeoVegas accepted £20,000 from a problem gambler who had stolen the money from his mother, and then bombarded him with emails encouraging him to keep betting.

Details of the case, uncovered by the Guardian, sparked renewed calls from campaigners and politicians for gambling companies to perform more rigorous checks before customers place bets.

The recovering addict, who is receiving treatment but could still face prosecution, had his account locked by LeoVegas in May 2018 after a customer service employee flagged up “concerning” communication during a live webchat.

The account was suspended days after LeoVegas received a £600,000 penalty from the Gambling Commission for separate incidents of accepting bets from problem gamblers.

Despite the suspension, sister companies in the LeoVegas group, including Pink Casino and Castle Jackpot, continued sending him marketing emails as often as four times in a day offering “free spins” and bonuses.

In January 2019, after months of receiving the emails, the gambler set up a new account with 21.co.uk, also part of the Leo Gaming group. He used the same name and email address but this time registered his mother’s debit card.

He proceeded to gamble away about £20,000 before 21.co.uk asked for ID verification and, on realising that he was using someone else’s card, eventually blocked his account.

Once again, though, sister companies in the Leo Gaming group resumed sending marketing emails from a host of its sites, offering free spins and refunds on losses.

As well as using his mother’s card without permission, the gambler had racked up thousands of pounds in debt from payday lenders including 247Moneybox, MyJar and Satsuma.

Labour’s deputy leader, Tom Watson, who is pushing for tighter controls on online gambling, said: “It makes no sense for gambling companies to be doing ID and affordability checks after gamblers have lost huge sums rather than before they’ve placed the bets.

“The whole system seems the wrong way round. We also need to see immediate action to scrap credit card betting and end the practice of bombarding gambling addicts with gambling ads.”

A Gambling Commission spokesman said: “We are absolutely clear with operators about the rules that they must follow to prevent and protect their customers from experiencing harm from gambling. Where we see evidence that those rules are not being followed, we will investigate.”

The case comes as the government conducts a review of whether regulations covering online betting should be tightened, including through stronger ID checks and rules that prevent gamblers from placing bets on credit.

Online casinos and bookmakers are not currently required to check whether gamblers can afford their habit before allowing them to place bets.

The Gambling Commission is understood to have collected evidence relating to the case and is examining whether LeoVegas breached the conditions of its licence to operate in the UK. LeoVegas declined to comment.

In 2018 the Gambling Commission forced LeoVegas to pay a £600,000 penalty for a series of transgressions after a review of the company’s licence to operate in the UK.

The majority of the failings related to self-exclusion systems, which allow gamblers to bar themselves voluntarily from placing bets with a company. The regulator found that 1,894 LeoVegas customers were sent marketing material despite having signed up to its self-exclusion scheme.

More than 400 customers were allowed to bet £200,000 over two months, without the company speaking to them first or applying a 24-hour “cooling-off” period.

Gambling lowlights

April 2019 Bookies withdraw new games after they are accused of trying to bypass laws cutting stakes on fixed-odds betting terminals from £100 a spin to £2.

December 2018 Ladbrokes is revealed to have paid £1m to victims of a problem gambler who had stolen from them, in return for a pledge not to inform the industry regulator.

November 2018 Three online casinos pay out £14m in regulatory penalties over failures in money-laundering and problem gambling controls.

May 2018 Leo Vegas receives £600,000 penalty for accepting bets from problem gamblers and sending them marketing material.

March 2018 SkyBet hit with £1m penalty for allowing gamblers who had self-excluded to keep betting and sending them marketing material.

August 2017 Online casino 888 fined a record £7.8m for failures in its duty to protect more than 7,000 vulnerable customers.