A climate change protest planned for the Sydney Harbour Bridge has been derailed after activists hit a roadblock in their effort to disrupt traffic.
Activists from Fireproof Australia vowed to light flares and walk across the bridge on Thursday as part of a "political prisoner protest" over the jailing of their colleague Andrew George, who is spending his birthday behind bars.
However, delays and a map with a poorly placed drop pin meant protesters scattered around the bridge and no protest took place.
Four of the group's members face up to two years in prison and fines of $22,000 after being arrested and charged for protesting on the bridge on Wednesday.
Thursday's demonstration hit its first hurdle when police visited members of the group and briefly detained them. Police confiscated candles the group had planned to use in their demonstration, Fireproof Australia spokeswoman Bonnie Cassen told AAP.
There had been communication issues as members arrived at different areas around the bridge.
"We had the pin on the wrong side of the bridge," Ms Cassen said.
A NSW Police spokesman told AAP officers had spoken to a handful of protesters who were on the bridge holding flags and who hadn't caused any disruptions. A police car was stationed at the northern end of the bridge and officers patrolled on foot.
George was jailed after staging his own protest on Sunday, running onto the pitch of an NRL match between the Cronulla Sharks and Wests Tigers brandishing a lit flare.
On Monday he was fined $440 and sentenced to three months in prison.
"It's a very harsh punishment for simply trying to call out the government's inadequacy on their policy on climate," Ms Cassen said.
Protests, petitions and speaking with politicians had not been effective in making governments take action on climate change, she said.
Fireproof Australia wants flood and bushfire survivors to be rehomed and the recommendations of the royal commission into the Black Summer bushfires to be fully implemented.
The four people involved in Wednesday's bridge protest were charged with multiple offences, including new charges targeted at activists.
The group parked a truck on the Cahill Expressway, blocking traffic near the south pylon, over Circular Quay and The Rocks.
Two of the group climbed onto the truck's cabin, holding a Fireproof Australia flag and lighting a flare, while another two glued themselves to the bridge.
The two women - a 31-year-old from Russell Lea and a 44-year-old from Robertson - and two men, a 36-year-old from Wentworthville and a 60-year-old from Cedar Creek, were arrested.
All four were refused bail and will appear in Central Local Court on Thursday.
