Three children's online games have been referred for a possible investigation by the advertising watchdog over concerns they encourage young users to spend money while playing.
The Competition and Markets Authority (CMA) said it was concerned that the games, which will not be named unless they are found to have breached advertising rules, could directly encourage children to buy, or ask their parents to buy, extra features.
It has referred them to the Advertising Standards Authority (ASA) to decide whether to investigate.
The CMA said the move was part of wider work to encourage the industry to address issues around how online and app-based games are advertised and paid for.
CMA senior director Nisha Arora said: "Seventy-five per cent of 10 to 15-year-olds in the UK play video games every day, so it's clear that they are a significant part of children's lives.
"We have seen some positive changes in business practices since we started looking at this sector.
"However, we are concerned that some games may directly encourage children to buy extra features during the game.
"We have therefore referred these games to the ASA to consider whether they breach the advertising codes."
ASA director of investigations Miles Lockwood said: "It's crucial that the ads children see, hear and interact with don't confuse, mislead or directly exhort them to make purchases.
"We welcome the CMA's referrals and will now establish whether the ads break the rules and to ensure children are treated fairly."