Video games that pressure children into spending hundreds of pounds when playing online face a crackdown from the Office Of Fair Trading.
Many computer, console and mobile phone games offer players the opportunity to buy extra lives or abilities when online.
It has led to many parents being left with huge credit card or mobile phone bills.
Now the Office of Fair Trading is threatening action against video game app-makers it finds in breach of consumer protection laws.
It says it is concerned about in-game charges, saying it has seen evidence of 'potentially unfair and aggressive commercial practices' after studying 38 popular titles.
It has not said which they are. Children might be particularly susceptible to such tactics, it warns.
It has now proposed new guidelines for developers which would apply to both apps and internet browser-based video games available via Facebook and elsewhere.
• Providing up-front information about the costs associated with a game before consumers download it
• Ensuring that gamers are not misled to believe they must make a payment to proceed if that is not the case, for example, if they could wait for a period of time instead
• Preventing the use of language or anything else that might exploit a child's inexperience, for example, implying an in-game character would be disappointed if they did not spend money • Making it clear how to contact the business if the gamer has a complaint
• Only taking a payment if the account holder provides 'informed consent', in other words a charge cannot be made because a password had recently been entered for something else
The OFT said some of the worst examples it had seen involved games that led children through an adventure but then withheld a promised reward until they spent money, and instances where the title made the player feel bad by telling them a virtual animal was 'ill' but could be made better if the gamer made a purchase.
"I don't think children are always aware that when they click 'yes' it's spending money," said Cavendish Elithorn, executive director at the OFT.
"Although parents can change their device settings to deal with some of that, many parents might not know, or it's only when they get the bill that they realise the setting was wrong.
"So, part of what we're keen to do is support parents in having the right tools to be aware of what their children are doing online."
He added that the OFT has the ability to take legal action against firms in the UK, and was working with partners in Europe, North America and Australia to try and get the same rules applied elsewhere.