Protesters gathered outside the Royal Courts of Justice on Wednesday as nine Insulate Britain activists were jailed for breaching a government injunction that banned them from blocking roads.

Eight were sent to prison for three or four months, while the ninth, Ben Taylor, was given a six-month sentence after a judge said his submissions to court were “inflammatory”.

Another of the jailed activists, Emma Smart, intends to go on hunger strike.

Raj Chada, representing the protesters, said: “With these prison terms, the long and honourable tradition of civil disobedience is under attack again.”

Insulate Britain have become increasingly active since summer, blocking busy roads – including motorways – to demand action from the government on home insulation and domestic energy waste.

A High Court injunction was handed to National Highways in September, which banned the group from obstructing traffic and prevented access to 4,300 miles of major A roads and motorways.

The jailed Insulate Britain activists admitted breaching the temporary injunction by taking part in a blockade at junction 25 of the M25 on 8 October.

Ana Heyatawin, 58, and Louis McKechnie, 20, were jailed for three months; while Ben Buse, 36, Roman Paluch-Machnik, 28, Oliver Rock, 41, Emma Smart, 44, Tim Speers, 36, and James Thomas, 47, all received four-month sentences.

The submissions made by 37-year-old Mr Taylor to the court on Tuesday were described by Dame Victoria Sharp as “inflammatory” and a “call to arms”, and he was therefore given a longer sentence of six months “to deter [him] from committing further breaches”.

The judge, sitting with Mr Justice Chamberlain, said there was no alternative to custodial sentences given that the group’s actions were so serious and they had made it clear they intended to further flout court orders.

“The defendants, or some of them, seem to want to be martyrs for their cause, and the media campaign surrounding this hearing appears designed to suggest this,” she said.

“We, however, have to act dispassionately and proportionately.”

The defendants and their supporters chanted “we are unstoppable, another world is possible” as they were led away following the sentencing.

Outside the Royal Courts of Justice, dozens of Insulate Britain activists gathered outside after the sentence was handed down.

Police officers watched on as the group, many of whom wore orange hi-vis vests, gave speeches, chanted and held large banners.

An Insulate Britain supporter read a statement outside the Royal Courts of Justice from the nine activists after their prison sentences were announced, saying they knew they faced jail when taking action but “could not stand by while the government betray the general public”.

“Over the last nine weeks, 174 ordinary people have held the government to account, asking that they deliver on their most basic of duties, to protect the British people, the economy and all we hold dear in our society,” it said.

“Your government has now chosen to act. It has chosen to imprison us for this demand.”

On Tuesday, the court heard how the 8 October protest – which the case was centred on – lasted for around an hour and a half and ended when the final two protesters, who had glued themselves to the ground, were removed by police.

It took place at the M25 junction at Waltham Cross in Hertfordshire.

Insulate Britain protests have been carrying on this month, with activists gluing themselves to roads outside parliament and blocking major roads in Manchester, Birmingham and Hertfordshire.

Additional reporting by Press Association