An online betting firm has been fined £442,750 for demanding ID from winning punters before it would give them the cash, while failing to carry out similar checks on potentially vulnerable people depositing money.

The Gambling Commission punished TonyBet, which is based in Estonia but has a licence to operate in Great Britain, for imposing unfair terms and failures in anti-money laundering and social responsibility measures.

The online casino told customers it had the right to request identification documents for “all withdrawals” despite not having insisted on those same checks earlier, potentially hampering withdrawals but not deposits.

Kay Roberts, the executive director of operations at the Gambling Commission, said: “Not only does this case illustrate our drive to clamp down on anti-money laundering and social responsibility failures, but it also highlights action we will take against gambling businesses who fail to be fair and open with customers.”

The fine highlights a practice that seldom attracts the attention of regulators. Gamblers have often alleged that strict checks are demanded of customers only when they win, with no equivalent scrutiny of whetherthey are suffering financial and mental harm.

The government is expected to publish a white paper on gambling reform within weeks, which could include much stricter requirements on operators to perform affordability checks after a string of cases where addicted gamblers lost huge sums.

Industry lobbyists, such as the Betting and Gaming Council (BGC), have repeatedly voiced opposition to the prospect of any measures that would be “intrusive”.

TonyBet will pay a fine of £442,750 after the transgressions were discovered during an audit in 2021. The company, which is not a member of the BGC, is an Estonia-based online casino carved out of a business founded by the Lithuanian businessman and professional gambler Antanas Guoga, known in the gambling world as Tony G. He no longer has any involvement in the business.

TonyBet also told winning punters their cash could be confiscated if they did not provide anti-money laundering documentation within 30 days. While the business demanded that winners went through such hurdles to collect, the commission found it failed to conduct adequate risk assessments of the business being used for money laundering and terrorist financing, or put controls in place to stop such activity.

Nick Goff, a professional sports bettor and former industry professional, said: “It is long overdue that firms were punished for this practice. It has been happening routinely at a lot of firms for a few years now.”

The Guardian has approached TonyBet and Guoga for comment.