According to the online discounts website, a further 25 percent admitted they had played the game with them.
The research also revealed that over half of parents (53 percent) let kids watch 15- or 18-rated films such as Borat and The Saw series, while 66 percent are okay with their children listening to music with explicit lyrics from artists such as Eminem and Jay-Z.
Mark Pearson, managing director of MyVoucherCodes.co.uk, said: "I was surprised by how many parents have actually allowed their child to watch a film, play a game or listen to music knowing that they weren't old to do so. I think that every child is different and what is right for one might not be for another, but I do think that ratings are there for a reason, so parents should execute some caution on deciding what they should expose their children to."
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