London - Britain said it would make social media companies such as Facebook and Twitter responsible for blocking or removing harmful content on their platforms.

A duty of care will be imposed to ensure all companies had systems in place to react to concerns over harmful content and improve the safety for their users, the government said.

"As the internet continues to grow and transform our lives it is essential that we get the balance right between a thriving, open and vibrant virtual world, and one in which users are protected from harm," Digital Minister Nicky Morgan and Interior Minister Priti Patel said in a joint statement.

The duty of care will apply to platforms on which user-generated content is shared, for example through comments, forums or video sharing, it said on Wednesday in its response to a consultation.

Policy will be developed to offer a higher level of protection for children than adults, the government said.