As Cardiff City’s Michael Chopra glanced around the dressing room, it was a painful reminder of his own private struggle with addiction, as well as a temptation to bet more: every one of his teammates was flaunting a betting company logo on their shirt.

Chopra, who spoke of his gambling problems this week, is among a number of well-known footballers – including Michael Owen, Wayne Rooney, Paul Merson, Peter Shilton, Andros Townsend and Dietmar Hamann – who have spoken of their struggles with gambling.

The most high-profile recent example is the Brentford and England striker Ivan Toney, banned by the FA for eight months in May after placing hundreds of bets, including on his own team.

Toney, who has since spoken of his addiction, must now rebuild a career that appeared to be on the verge of exploding, with the striker seen by some pundits as a thrilling prospect, able to lead the line for England.

The West Ham midfielder Lucas Paquetá is under investigation by the Football Association in relation to betting activity. The nature of the allegation has not been revealed. Harry Toffolo was recently given a five-month suspended ban after admitting to breaking betting rules.

Other players to fall foul of the rules, in 2020, include the Newcastle United and England right-back Kieran Trippier, fined and suspended for disclosing details of his upcoming transfer to a friend – and the former Liverpool striker Daniel Sturridge.

The FA introduced strict new rules on betting before the 2014-15 season. On the face of it, the rules are simple. To paraphrase: anyone involved in the game must not bet on any football match, anywhere in the world.

However, the FA was mindful of the fact that some club owners were inherently involved in betting, via their business interests. These included the Coates family behind Stoke City and Bet365, as well as the Brighton owner Tony Bloom and Matthew Benham – a former employee of Bloom and the owner of Brentford FC.

The FA feared that there could be an “adverse impact” on up-and-coming clubs such as Brentford and Brighton – which owed their ascendancy to their betting entrepreneur bosses – if it enforced a strict separation between football and gambling.

So an exemption was drawn up for “participants” in football, aimed at club owners. The FA says the policy is not secret, and that anyone who needs to know what it says has a copy. However, it has refused to disclose details of it, leaving fans in the dark about the small print.

Those bound by the policy must submit an annual declaration to ensure they are meeting all the required conditions. They are also obliged to report any suspicious betting activity on English football that they learn of, by virtue of their position with the betting company, to the FA.

Perhaps the most important condition is that they must not have any direct involvement in, or passing on of information related to, the setting of odds, the determining of markets, or the selection or placing of individual bets on football.

Club owners who have been asked, including Benham and Bloom, say that they comply with this policy. The FA has yet to publish it.

In the meantime, footballers continued to be punished for breaching rules that appear to be much clearer, raising questions about why there is one rule for them and another one, as yet unpublished, for the people who pay their wages.