The Government is to introduce tougher powers to deal with climate change activists who have caused chaos on the roads by blocking motorways.

At the Tory Party conference in Manchester, Home Secretary Priti Patel will warn that protesters who block the highway could face unlimited fines and up to six months in jail.

Police are also to be given the powers to stop and search activists for “lock-on” equipment used to prevent them from being moved.

The move follows days of protests by the Insulate Britain group, which has staged sit-down demonstrations on a series of key arteries around London, including on the M25, M1 and M4.

The Government on Saturday obtained a fresh injunction banning the group from obstructing traffic and access to motorways and major A roads in and around the capital.

The new powers to be announced by Ms Patel will be included in the Police, Crime, Courts and Sentencing Bill currently going through Parliament.

Ministers argue that while they accept the right to protest, the current offence of obstructing the highway, which carries a maximum fine of £1,000, does not reflect the seriousness of the disruption such actions cause.

Ahead of her conference speech, Ms Patel said: “The right to protest is a fundamental principle of our democracy but we will not tolerate guerrilla tactics that obstruct people going about their day-to-day business.”

Prime Minister Boris Johnson added: “This Government will always stand on the side of the law-abiding majority and ensure the toughest penalties possible for criminals who deliberately bring major roads to a standstill.

“We will give the police the powers they need to stop their reckless and selfish behaviour.”