An arson manual and tips on making petrol bombs have been shared in posts on Telegram, a messaging platform. Groups have also listed details of immigration lawyers and advice centres across England and have told their members to attack them mid-week.

The news comes in the wake of an attempt by rioters to burn down two migrant hotels in Rotherham, South Yorkshire, and Tamworth, Staffordshire, on Sunday. Rioters attacked the police with fireworks, urine, animal faeces and stones. In Staffordshire they used petrol bombs to start a fire in the building.

Telegram users shared instructions on how to make petrol bombs and an “arson manual” made by National Socialism/White Power Crew, which anti-fascist researchers Red Flare said was a Russian-Ukrainian neo-Nazi group.

Nick Emmerson, the president of the Law Society of England and Wales, said: “We have serious concerns about the safety and wellbeing of our members following names and addresses of a number of solicitors’ firms and advice agencies being shared on a list of targets for further protest and violence this week.

“I have written to the prime minister, lord chancellor and home secretary today asking that the threats against the legal profession are treated with the utmost seriousness.”

Counterterrorism experts said prosecutors may be considering terrorism charges if the violence escalates.

One said: “The public order command of the Met will certainly be liaising around the charging threshold for terrorism, we’re not far away from it, but there are a multitude of other offences they will consider first.”