British ISPs moving towards "opt-in" system for Internet pornography

The measures will be unveiled on Tuesday as David Cameron hosts No 10 meeting with the Mothers’ Union, which earlier this year produced a raft of proposals to shield children from sexualised imagery.

The prime minister is expected to announce other moves in line with the Christian charity’s review, such as restrictions on aggressive advertising campaigns and certain types of images on billboards.

There will also be a website, Parentport, which parents can use to complain about television programmes, advertisements, products or services which they believe are inappropriate for children.