Youngsters are asked to help cartoon girl Goldie decide if she should get enhancement injections.
Before that, they must remove hair from her upper lip and add lip gloss before measuring her face and drawing on it where surgery should take place.
The main image advertising the online medical simulation game shows a teenage girl having her plumped lips injected with a needle as her eyes water.
Expert Mandie Dransfield, of MD Medical Aesthetics, said: “This game is very disturbing and wholly inappropriate.
“Children are being increasingly exposed to damaging body image because of TV and social media but this game could lead to a child seeking out something they had no idea existed before they clicked the ‘Play’ button.”
Carolyn Bunting, boss of Internet Matters, added: “It’s worrying that a game like this can be so easily accessed by children.
"The content is potentially damaging to self esteem and body image as it can reflect unrealistic beauty standards.
“It’s vital that the forthcoming Online Safety Bill tackles legal but harmful content to children online, particularly, content that negatively impacts body image.”
There are no age checks for players of Goldie: Lip Injections — just a disclaimer in tiny type saying “By clicking ‘Play’ you declare you are 16 years old”.
It is made by US firm Sisi Games and is one of hundreds on games.co.uk. It is on the girls section of its website.
Dutch firm Spil Games, which owns the games on the site, were approached for comment.
In the game plays must remove hair from Goldie's upper lip and add lip gloss before measuring her face
Girls then have to draw on where the surgery should take place