The Independent Television Commission (ITC) has issued a proposed programming code which insists that all programmes which start at 9pm and run until 10pm be "suitable for family viewing".
ITV is particularly worried about the plan because the timing of the News at Ten would mean it could not start running adult programmes until 10.30.
The ITC regulates programmes on ITV, Channel 4 and cable and satellite. The watershed prevents nudity, sex or violence being shown before 9pm.
ITV is also angry because the watershed on cable and satellite channels is already lower at 8pm.
The draft plan also proposes that no one should be portrayed smoking in programmes unless there is "strong editorial justification for inclusion".
"Taken literally that would mean we couldn't show Casablanca before 9pm because Humphrey Bogart smokes, for example," said an ITV spokeswoman.
A new clause would also ban the depiction of drug-taking as "problem free and glamorous".
An ITV source told the industry magazine Broadcast: "The ITC has gone too far. It has a sanitised view of life. They are Americanising television."
The ITC defended the proposals and said yesterday they were intended to generate discussion. "We are not saying there will never be films or dramas starting before 9pm which resolve with a certain amount of violence just before 10pm, only that it should not become a regular thing," said a spokeswoman.
However, ITV is drawing up a strongly worded response opposing the plan.
The ITC has issued warnings to broadcasters in the past for starting programmes on the 9pm watershed with adult scenes. Cracker was once censured for opening with a rape scene.Reuse content