The Gambling Commission raised the issue in a statement explaining that promoting fantasy football on Facebook or Twitter may require a licence.

The regulator said: “Advertising, when it comes to gambling, includes doing anything that encourages someone to gamble or provides information about gambling facilities so that it will increase use. This also includes Twitter or Facebook posts, whether public, or private or within groups. Promoting a fantasy football league in this way could mean it is being operated in the course of a business and need an operating licence.”

Whether a fantasy football league needs a pool licence is determined by the number of paying entrants and even leagues that are not run for profit are subject to the rules.

Ben Haden, programme director at the Gambling Commission, said: “We want to ensure that those organising these leagues — whether it’s between friends, work colleagues or otherwise — are aware of the legalities and do not breach gambling rules.”