CSI has spawned a spin-off

The show is the most popular programme in the US but was criticised by The Parents Television Council for subject matter including cannibalism and sex clubs.

Melissa Caldwell, research director for the watchdog which monitors violence and sex on TV, also complained about the time the show was aired.

The drama's regular slot is 9pm on Thursdays but repeats of the show are occasionally shown at 8pm when more children are likely to be watching, said Caldwell.

The CBS network series revolves around forensic investigations which often stumble upon some unsavoury situations.

But Caldwell said: "There are ways you can deal with these issues without having to be as graphic."

Spin-off

A spokesman for CBS said that while the PTC's goals were noble, he was thankful that 26 million viewers a week disagreed.

CSI usually tops the weekly prime-time ratings in the US and has created a spin-off series called CSI :Miami.

Both shows also air in the UK on Five (formerly Channel 5) after the watershed on Tuesdays and Saturdays.

Five has bought up a number of US shows including Alias and The Shield.

CSI: Crime Scene Investigation, averaged 26.2 million viewers over the most recent US TV season, which ran from September last year to May 2003.

The drama has been nominated for this year's Primetime Emmy Awards in the outstanding drama series category and for lead actress in a drama (Marg Helgenberger).