According to a survey from the Advertising Standards Authority, there were no breaches among 312 press, 31 radio, five outdoor ads, 28 examples of direct marketing and eight circulars it surveyed. But six of the 56 TV ads and one of the 344 internet ads studied broke the code.
Four of the TV ads were by one online casino and poker company, thought to be Intercasino, which the ASA found would appeal to children.
Lord (Chris) Smith of Finsbury, the former culture secretary who chairs the ASA, said: "This shows self-regulation is working, and is working robustly. It's a pretty clean bill of health, but there is a need for constant vigilance."
Smith added: "We followed up on all the ads that were in breach and the advertisers agreed that they would not repeat them."
The Gambling Act 2005 gave new freedoms to bookmakers, betting exchanges, casinos and lotteries to advertise, prompting concern from some campaigners, including religious groups.