BetFred, one of Britain’s most familiar betting brands, has been accused of backtracking on a pledge to honour outstanding customer balances in the failed online bookmaker MoPlay after buying MoPlay’s customer list from a liquidator in Gibraltar last month.

MoPlay stopped trading in February after its parent company, Addison Global, went into liquidation. Customers with funds in their accounts were unable to withdraw their money but, after an auction for the customer list, a statement from MoPlay in mid-March revealed it had been “able to secure an arrangement whereby another operator will honour your cash balance, so that you can withdraw your funds and continue to play”.

It added that if customers were registered in the UK or Ireland, “BetFred will be in contact with you with details of how to set up an account with them and access your balance”.

Around 180,000 MoPlay accounts are understood to have migrated to BetFred a few weeks ago. However, it is unclear how many accounts did not make the switch, and several former MoPlay customers have approached Justice4Punters, an online forum that campaigns on issues affecting gamblers, to complain that their balances did not shift to BetFred despite their having accounts.

The accounts in question appear to have been “restricted”, either by BetFred or MoPlay, because the customers were considered unprofitable by the operator. The Guardian has seen details of two such accounts, including one with a MoPlay balance of £27,000, which did not migrate to BetFred, while a third former customer of MoPlay, with a balance of £680, has complained that his BetFred account, which had made a lifetime profit of around £300, was closed by the bookmaker two days after the announcement of its deal to buy MoPlay’s customer list.

“We’ve received a fair number of complaints,” Brian Chappell of Justice4Punters said. “All the complaints seem to have one thing in common, they have restricted betting accounts, be that with MoPlay and/or with BetFred. From what we’ve been sent, it’s certainly not clear to J4P why these customers are being treated differently, except it all seems rather commercially convenient.”

A BetFred spokesman said this week that the firm “could not confirm how many accounts did not migrate from MoPlay, as this information is not within our knowledge”. The spokesman also said the bookmaker had “successfully migrated circa 180k customers from MoPlay to BetFred, these customers reflect eligible customer accounts and specifically excluded self-excluded or frozen accounts. We did not conduct any due diligence on the profitability of individuals in the MoPlay customer database nor did we close any BetFred accounts to prevent migration of MoPlay balances.

“Our actions to date are 100% in accordance with the terms of the contract with the liquidator and for those customers who did not migrate we are directing them to the liquidator to submit a claim in the liquidation.”

The problems faced by some former MoPlay customers also highlight the fact that the Gambling Commission allows operators to choose the level of protection – high, medium or not protected – afforded to deposits in the event of a firm going bust. This, the commission says, is “because of the potentially high costs which may be passed on to the consumer”.

The Horseracing Bettors Forum, an independent group which represents punters’ interests, pointed out last month that only eight of 64 firms it surveyed offer a cast-iron guarantee that deposits will not be treated as part of the assets if it goes into liquidation. MoPlay opted for the lowest level of protection.

“Our inquiries into the MoPlay situation earlier this year established there was a significant risk that none of their customers would have received their funds,” a spokesperson for the Gambling Commission said this week. “Putting the interests of consumers first, we concluded that the sale of the customer database was the best option available for the vast majority of customers in what was an unusual and difficult situation.”