“Children are playing a game that encourages them to have sex with prostitutes and then murder them,” the senator and former first lady said. “This is a silent epidemic of media desensitisation that teaches kids it’s okay to diss people because they are a woman, they’re a different colour or they’re from a different place.”

Clinton, who is expected to seek the Democrats’ presidential nomination in 2008, has teamed up with two archconservative Republican senators, Rick Santorum and Sam Brownback. They want President George W Bush and Congress to launch a $90m (£48m) investigation of the impact of electronic media on children’s “cognitive, social, emotional and physical development”.

Clinton has been declaring her shared values with Republicans on issues as diverse as abortion and the war on terrorism. Her campaign against video game violence has alarmed right-wing opponents of her expected bid for the White House.

L Brent Bozell, president of Parents Television Council, an influential conservative watchdog, said: “Hillary’s would-be Republican competitors had better take notice. She is successfully outflanking them on a hugely important issue she intends to make her own.”

Clinton’s attack was delivered at a childcare symposium hosted by the Kaiser Family Foundation, which studies children’s leisure habits.

Its latest research shows that daily use of computer and video games by children has virtually doubled since 1999 to nearly two hours. Violent games are a favourite with teenage boys.

Researchers from the University of Oklahoma recently found that two-thirds of school fights were instigated by regular video game players, but only 4% were started by children who had never played such games.

Other studies showed that violent games would not cause serious problems in healthy families, but could do so in families where children were left alone for many hours.

Dick Morris, an adviser to Bill and Hillary Clinton in their White House years, said that Hillary was following a playbook he had devised with her.

Polls undertaken for her had shown that women were perceived as better than men on issues involving children and education, while men led on foreign policy.

She was “using that stereotype to help her candidacy”, Morris said, by pursuing family issues while becoming “hawkish” on defence.

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