Theresa May and Donald Trump have agreed to jointly launch a string of cyber-attacks against Isil designed to “eradicate” the extremist group.

The pair discussed how cyber-warfare can help fulfil Mr Trump’s pledge to wipe the jihadists “from the face of the earth” during talks in the White House.

The Sunday Telegraph understands Whitehall is preparing to step up “offensive” online attacks to cripple Isil's infrastructure and steal valuable information.

Britain and America will also increase efforts to take down beheading videos and other extremist content posted on the internet that radicalises youngsters.