David Nixon, 36, was found guilty at Inner London Crown Court for causing a public nuisance by blocking the junction of Bishopsgate and Wormwood Street in the capital on October 25, 2021.
His group had stopped traffic with around 30 others as part of Insulate Britain’s campaign of civil resistance.
At Tuesday’s sentencing, Judge Silas Reid questioned Mr Nixon about his future intentions and in particular asked whether he intended to continue in civil resistance.
He indicated that this would determine whether a suspended or a custodial sentence should be given.
In his mitigation statement, Mr Nixon said: “I will start by making clear that I will be continuing on, I will continue to take action that may lead to my arrest and potential imprisonment.
“Prison is not a deterrent, merely a pause - I am justified in doing this as we are facing an existential threat to humanity, and our government is actively making things worse.
“It’s abhorrent, it needs resisting and I am right in my actions.
“I totally appreciate that our decision to block roads disrupts people’s days, especially so given how fragile the economy is.
“The prosecution claimed that 8,500 people were disrupted by bus diversions on the October 25, 2021.
“They argued that that is significant and substantial - coincidentally, in the year 2020, it was estimated that 8,500 people died over winter due to living in cold homes.
“At least our members are trying, we’re attempting to force change by doing something and I will continue my efforts.”
Judge Reid, who handed Mr Nixon a five-week sentence, questioned why Insulate Britain would continue their campaigns.
An Insulate Britain spokesperson added: “As with all public nuisance trials at Inner London Crown Court, Mr Nixon was subject to Judge Reid’s gagging order during the trial.
“Reid’s ruling prevents Insulate Britain supporters from truthfully defending themselves in court by banning them from mentioning fuel poverty, the climate crisis or civil resistance when defending their actions in front of the jury.
“In the 12 Insulate Britain jury trials for public nuisance charges to date, two trials have resulted in a hung jury, two trials have resulted in acquittals, six have resulted in a guilty verdict and two have been deferred.
“The Crown Prosecution Service (CPS) has applied for retrials in the two cases where the jury failed to reach a majority verdict - this is despite the Code for Crown Prosecutors which states that the CPS must only bring cases where there is a ‘realistic prospect of conviction’.
“The current rate of successful convictions of Insulate Britain supporters brought to trial for a charge of public nuisance is 50 per cent.”