Customers of major internet service providers will have to "opt-in" to receive adult content online as part of measures aimed at ending the sexualisation of children.
Subscribers to BT, Sky, Talk Talk and Virgin will not be able to access porn sites under the new plans, to be announced by David Cameron today.
The Prime Minister is also expected to announce the creation of a new website called Parentport, on which parents can complain about any TV programme, advertisement or product that they feel is inappropriate for children. The move comes in response to a report by Reg Bailey, chief executive of the Mothers' Union charity, which recommended shielding children from sexualised imagery.
Other measures are expected to include restrictions on billboards of scantily-clad models.