Two climate protesters are in jail for blocking traffic lanes on a major Melbourne freeway, causing significant rush-hour delays.

Deanna ‘Violet’ Coco, 33, from NSW and 51-year-old Bradley Homewood from Williamstown pleaded guilty to two counts of public nuisance by obstructing motorists and obstructing police and emergency service workers on Tuesday.

Both were sentenced to 21 days imprisonment.

Their co-accused Joseph Zammit, 68, from Melbourne, also pleaded guilty to the same charges.

He was released on bail on the condition that he not attend unlawful protests or undertake any unlawful actions during a protest and not associate with Coco and Homewood.

The members of environmental action group Extinction Rebellion parked a truck on the West Gate Bridge about 7.45am on Tuesday. They climbed on top, unfurling banners that read “declare a climate emergency” and “climate breakdown has begun”.

Police alleged they set off flares while on top of the truck.

The protest caused a traffic gridlock with three city-bound lanes blocked and delays stretching about 30 kilometres.

“The ramifications of their actions caused massive catastrophic inconvenience and delay to thousands of members of the public,” a police prosecutor told court.

Officers used a cherry picker to arrest and lower the trio safely at 9.45am after they refused to get off the truck. Significant traffic delays persisted after the lanes were reopened.

Zammit defended his group’s action in Melbourne Magistrates Court, saying they were concerned about people’s futures.

“What they suffered today is nothing compared to what’s going to happen in the future,” he said.

“What we’re actually doing is a service to the community.”

But Magistrate Andrew McKenna chastised the activists, saying the actions are hard to justify.

“It’s not about anarchy. It’s about an ordered society – the proper democratic way,” he said.

“Whether someone has a worthy cause or not, you’ve got to work within the law to promote it and if you don’t, you’re liable to be punished.”

Homewood said he was forced to act after being driven to a state of despair over the existential crisis faced in a climate breakdown.

“I feel like I have no choice left,” he said.

“I’ve tried all the conventional methods of campaigning and nothing has worked.

“We view what we do as a proportional response to the inaction from governments of the world.”

He defended his actions saying non-violent protests are vilified at the time but activists ended up vindicated in the future.

McKenna said the protesters would have produced the opposite reaction they desired among most of the community.

Coco has had previous run-ins with police in Victoria, NSW and Western Australia for her activism. She was jailed for 13 days after blocking a lane of the Sydney Harbour Bridge during morning peak hour in 2022.

Police accused Coco of making a career out of being a public nuisance. As he jailed Coco, Magistrate McKenna said she was completely uncaring of the victims of her actions.

“She basically put her own interests and her own cause ahead of the interests of others in the community – many more people than just she and two others,” he said.

Zammit is due back in court on April 16.

-AAP