Facebook has been criticised by disability charities for hosting adverts across the platform featuring the word "retard".
The adverts for the game Hustle Castle: Medieval Life featured characters with the heading "Level 1 Retard", reported digital content site Digiday.
The adverts also featured on the social network Instagram, which is owned by Facebook.
The social media giant has yet to comment.
The game which caries a 9+ age rating on Apple's App store, allows players to run a castle and start battles. It is developed by the Dutch company My.com, which is owned by the Russian internet company Mail.Ru.
"It's pretty surprising that in 2018 the creators of a game for children are using such antiquated language in their advertising materials," said Richard Lane, spokesman for the disability charity Scope.
Leroy Binns, who has a learning disability and works for the charity Mencap, told the BBC about his own experiences with the word.
"I have been called this and it is one of the most hurtful things someone with a learning disability can be called. It makes us feel like we are worthless and people think less of us," he said.
"This company should take the word down and Facebook and Instagram should know better and make it clear this language is not allowed."
A spokesman for My.com has apologised for the advert, which he said was created in Russia.
"This was a poor judgement call without the proper knowledge of the language and disconnected from the local market. We apologise for the offence and will take steps to improve our advertisement choices." he said.
The company confirmed it had pulled the adverts from both Facebook and Instagram.