The government plans to order internet service providers (ISPs) to block extremist websites identified by a specialist unit set up to identify content too dangerous for publication online.
The plans are part of measures for tackling extremist and terror content online to be announced soon, according to security minister James Brokenshire.
The government wants to follow the model used to counter child abuse online where the Internet Watch Foundation identifies illegal child abuse images that ISPs are asked to block, according to the Guardian.
Under the anti-terror plans, a specialist unit will be empowered to order ISPs to block websites, but ISPs are likely to oppose the plan because it could compromise freedom of speech, the paper said.
ISPs and search engine operators Google and Microsoft recently agreed to block child abuse images, post warnings and provide links to advice sites.
From 2014, all customers of the major broadband companies will be asked whether they wish to install filters that block violent or adult content.
The filters will be activated automatically for new customers who will have to ask if they want them to be turned off.
The Guardian cited unnamed sources as expressing concerns about blocking material that some customers may feel entitled to access.
ISPs want the government to introduce a process for testing what content is illegal and a robust appeals process, arguing that political incitement is not as clear cut as child exploitation.
The government’s plans signal a shift to a more proactive approach to content deemed to be illegal, with the Internet Watch Foundation piloting methods of actively searching for abusive images.
Earlier this month, prime minister David Cameron said UK and US intelligence agencies will help fight child abuse images on the dark web that is inaccessible to search engines.
Cameron said he was confident of progress after talking to internet service providers (ISPs) and the National Crime Agency (NCA) team that will work with US counterparts to apply the best expertise.
Asked about the potential invasion of privacy that would result from the move, he said: "People understand that a crime is a crime whether it's committed on the street or the internet."
On 9 December the UK policing minister and the US assistant attorney general will co-chair the first meeting of the taskforce to combat online child sexual exploitation crimes.
More on UK internet crackdown
- Microsoft launches UK child porn warning
- UK to block online porn by default
- PM calls meeting to tackle online porn
- PM urged to criminalise internet rape porn
- Fight against online child porn goes overseas