The first-person shooter has attracted criticism for its violent content, in particular one checkpoint scene that is preceded by in-game warnings.
Vaz told the Daily Mail: "I am absolutely shocked by the level of violence in this game and am particularly concerned about how realistic the game itself looks."
Following a question from Vaz in the House of Commons, Watson replied: "I have seen the content of the video game. It is unpleasant, although no worse than in many films and books. The game carries a content warning. It is an 18-plus game, and carries the British Board of Film Classification 18-plus rating as well.
"Does the Minister agree that it would be better for Members of the House to support the many thousands of game designers and coders, and the many millions of game users, rather than collaborating with the Daily Mail to create moral panic over the use of video games?"
Vaz later told the BBC: "Nobody is trying to stop anyone over the age of 18 purchasing this game."
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