The federal government is being urged to push internet service providers to automatically block pornography sites unless customers opt in, following a similar move in Britain.

British Prime Minister David Cameron said "family friendly" filters would mitigate the hardcore images he said were "corroding childhood".

The Australian government abandoned its mandatory internet filter policy last year amid criticism it would not be effective, would be costly, slow down services and involved too much censorship.

Australian child welfare advocates have renewed calls for greater internet regulation, saying the British plan would offer youngsters more protection online. But opponents said the Cameron push was likely to fail, and that a compulsory filter was a "dead issue" in Australia.

Australian Christian Lobby general manager Lyle Shelton said the latest proposal would not prevent adults from viewing pornography, but would provide an extra shield for young people.