William Hill has been given a slap on the wrist for an advert which the watchdog concluded was "misleading".
Following a complaint, the Advertising Standards Authority (ASA) reviewed a TV ad which offered punters a 15 per cent free bet bonus if their horse won by two lengths or more.
Small print at the bottom of the screen said the offer was only available on races with six or more runners. But the ASA said this was contradictory to the voiceover, which said the offer could be on "any live ITV flat race".
The watchdog also noted that runners can sometimes drop out of races at the last minute, meaning that a bonus attached to a bet might stop being eligible without the consumer becoming aware.
"The ad must not appear again in its current form," the ASA concluded. "We told William Hill to make significant conditions to offers in their ads clear and to ensure that they do not contradict the claims they qualified."
William Hill responded to the complaint by saying it was aware of the rules, and had "considered the information that the promotion only applied to races with at least six runners was readily available for consumers to make an informed choice about whether to participate in the offer".