Anyone who posted on social media assisting or encouraging the disorder on Britain’s streets in recent days could be prosecuted over the violence, even if they were were not at the scene, a legal expert has warned.

Mark Jones, partner at law firm Payne Hicks Beach, said individuals “do not need to be present when the crime itself is carried out, yet can be as guilty as the person who commits the crime itself”.

The warning comes as Sir Keir Starmer said anyone whipping up violence online will face “the full force of the law”.

After chairing an emergency meeting of the Cobra committee on Monday morning, the Prime Minister said “the criminal law applies online as well as offline”.

Mr Jones added: “People who assist or encourage another, or others, to commit a crime are known as accessories or secondary parties.

“They do not need to be present when the crime itself is carried out, yet can be as guilty as the person who commits the crime itself.

“In other words, you have a principal who carries out the offence and the secondary party who assists or encourages the commission of the offence by the principal.

“Secondary liability principles can be applied to most criminal offences, with offences of violence and public order being common examples.

“Social media provides a platform for people to misbehave and to commit acts which are criminal. It is necessary to look beyond the use of social media as the medium and to the offence being committed.”

Offences around incitement in UK law were in place long before the social media age, and fall under the Public Order Act 1986, but stronger measures are on the way in the form of the Online Safety Act, which passed into law in 2023 but is yet to come into full effect.

It will require social media firms to take more robust action against illegal and harmful content and activity on their platforms.

Earlier on Monday, Home Secretary Yvette Cooper said the Government would not tolerate “armchair thuggery” and that social media platforms needed to take responsibility for the spread of online misinformation which has fuelled much of the disorder.

Social media sites have been criticised for not doing enough to tackle the spread of disinformation, particularly since the stabbings in Southport last week.

None of the major platforms has yet commented on the misinformation and disorder in Britain, but in their site rules many commit to working with police and other law enforcement agencies as part of their response to harmful content.