New rules under the 2005 Gambling Act will allow online sites to advertise on television and radio for the first time.
The laws, to be announced today, will also allow regular casinos and betting shops to pull in punters using broadcast ads from September.
However, the Advertising Standards Agency will still police the promotional content from gambling companies.
Under the new laws, adverts will not be allowed to target minors or promote gambling as making the user more attractive or sexually successful.
Advertisers will also be forbidden from presenting gambling as a way out of financial trouble, or encouraging behaviour that might lead to financial, emotional or social harm.
The adverts cannot be shown during programmes specifically aimed at children, and the actors involved must appear to be at least 25 years old.
Online casinos and sports betting sites had previously been allowed to advertise only on other websites, billboards or through sponsorship.
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