Theresa May’s plans to crackdown on online extremist material by fining technology companies that fail to remove it have been criticised by the Government’s anti-terror watchdog.

Max Hill, the Government’s independent reviewer of anti-terror legislation, reportedly said he did not see how “criminalising” online giants for failing to “do enough” would work as he questioned how ministers would define adequate and timely action.

His comments are likely to come as a blow to the Prime Minister who put plans to punish companies like Facebook, YouTube and Google if they fail to remove extremist propaganda and terrorist material from their platforms at the heart of her response to recent terror attacks in the UK.