Culture Secretary Tessa Jowell has said television quiz phone-ins which charge for calls could be classified as gambling.

Broadcasters currently get around regulations by letting viewers to take part for free on the internet. However, there is some concern they are not advertising the alternative methods sufficiently.

Now, in an official document, Jowell has suggested the rules are being reviewed and tightened up. She said the Gambling Act 2005, which comes into force in September, will reclassify phone-ins without "well-publicised" free methods as lotteries.

The authorities could then use their "full powers to prosecute and shut down anyone who does not have the required licenses or permission to run the lottery".

Jowell also said Ofcom and ICSTIS would soon announce "significantly strengthened regulation" in the area of television phone-ins.

The announcements follow a number of questions over misuse of premium-rate phone-ins and concern from MPs.