Environmentalists occupied five bridges in London on Saturday to highlight government “inaction” on climate change.

The Extinction Rebellion group said more than 6,000 people blocked the crossings at Blackfriars, Waterloo, Westminster, Lambeth and Southwark from around 10am.

At least 85 activists were arrested for obstruction of the highway and bail act offences during the demonstration.

The Metropolitan Police said the protests caused “significant traffic disruption” in central London before all the bridges were reopened by around 4pm.

Activists then moved on to a rally in Parliament Square, where officers moved in to surround the statue of Winston Churchill after a green flag was attached to his walking stick.

Comparing themselves to US civil rights campaigners, the protest group said radical action was necessary to “raise the alarm” about the looming climate crisis.

“We represent a huge number of concerned citizens – scientists, academics, politicians, teachers, lawyers, students, children, parents, and grandparents,” said organiser Tiana Jacout.

Extinction rebellion: Climate change protesters block London bridges Show all 25 1 /25 Extinction rebellion: Climate change protesters block London bridges Extinction rebellion: Climate change protesters block London bridges Demonstrators block Westminster Bridge in central London to show anger at government inaction on climate and ecological issues AFP/Getty Extinction rebellion: Climate change protesters block London bridges A pro environment protester is arrested by police on Lambeth bridge in London EPA Extinction rebellion: Climate change protesters block London bridges Organised by Extinction Rebellion, the protest is part of many taking place this weekend to bring attention to political inaction on issues of pollution and climate change Reuters Extinction rebellion: Climate change protesters block London bridges A demonstrator puts tape on her mouth as she takes part in a pro-environment protest blocking Westminster Bridge in central London on November 17, 2018, calling on the British government to take action on climate and ecological issues. - Organized by Extinction Rebellion, the protest is part of many taking place this weekend to call for action on what they describe as a climate and ecological emergency. Extinction Rebellion demands that the UK government reduces to net zero greenhouse gas emissions by 2025 and creates a citizens assembly to oversee changes in environmental policies. (Photo by Tolga AKMEN / AFP)TOLGA AKMEN/AFP/Getty Images TOLGA AKMEN AFP/Getty Extinction rebellion: Climate change protesters block London bridges Organised by Extinction Rebellion, the protest is part of many taking place this weekend to bring attention to political inaction on issues of pollution and climate change PA Extinction rebellion: Climate change protesters block London bridges Demonstrators on Blackfriars Bridge PA Extinction rebellion: Climate change protesters block London bridges Police with demonstrators on Blackfriars Bridge PA Extinction rebellion: Climate change protesters block London bridges Demonstrators take part in a pro-environment protest as they block Westminster Bridge in central London on November 17, 2018, calling on the British government to take action on climate and ecological issues. - Organized by Extinction Rebellion, the protest is part of many taking place this weekend to call for action on what they describe as a climate and ecological emergency. Extinction Rebellion demands that the UK government reduces to net zero greenhouse gas emissions by 2025 and creates a citizens assembly to oversee changes in environmental policies. (Photo by Tolga AKMEN / AFP)TOLGA AKMEN/AFP/Getty Images TOLGA AKMEN AFP/Getty Extinction rebellion: Climate change protesters block London bridges epa07172610 Pro environment protesters block Westminster bridge in central London, Britain, 17 November 2018. Reports state that the protest organized by Extinction Rebellion group is planning to close five main bridges across the river Thames, seeking to bring attention to political inaction on issues of pollution and climate change. EPA/FACUNDO ARRIZABALAGA FACUNDO ARRIZABALAGA EPA Extinction rebellion: Climate change protesters block London bridges A demonstrator is led away by police on Blackfriars Bridge PA Extinction rebellion: Climate change protesters block London bridges Environmental campaigners from the direct action group Rebellion demonstrate on Westminster Bridge in central London, Britain, November 17, 2018. REUTERS/Peter Nicholls PETER NICHOLLS Reuters Extinction rebellion: Climate change protesters block London bridges Police with demonstrators on Westminster Bridge in London for a protest called by Extinction Rebellion to raise awareness of the dangers posed by climate change. PRESS ASSOCIATION Photo. Picture date: Saturday November 17, 2018. See PA story PROTEST Rebellion. Photo credit should read: John Stillwell/PA Wire John Stillwell PA Extinction rebellion: Climate change protesters block London bridges Environmental campaigners from the direct action group Rebellion demonstrate on Westminster Bridge in central London, Britain, November 17, 2018. REUTERS/Peter Nicholls PETER NICHOLLS Reuters Extinction rebellion: Climate change protesters block London bridges Demonstrators take part in a pro-environment protest as they block Westminster Bridge, near the Houses of Parliament in central London on November 17, 2018, to show anger at government inaction on climate and ecological issues. - Organised by Extinction Rebellion, the protest is part of many taking place this weekend to bring attention to political inaction on issues of pollution and climate change. (Photo by Tolga AKMEN / AFP)TOLGA AKMEN/AFP/Getty Images TOLGA AKMEN AFP/Getty Extinction rebellion: Climate change protesters block London bridges Demonstrators take part in a pro-environment protest as they block Westminster Bridge in central London on November 17, 2018, to show anger at government inaction on climate and ecological issues. - Organized by Extinction Rebellion, the protest is part of many taking place this weekend to bring attention to political inaction on issues of pollution and climate change. (Photo by Tolga AKMEN / AFP)TOLGA AKMEN/AFP/Getty Images TOLGA AKMEN AFP/Getty Extinction rebellion: Climate change protesters block London bridges Police with demonstrators on Westminster Bridge in London for a protest called by Extinction Rebellion to raise awareness of the dangers posed by climate change. PRESS ASSOCIATION Photo. Picture date: Saturday November 17, 2018. See PA story PROTEST Rebellion. Photo credit should read: John Stillwell/PA Wire John Stillwell PA Extinction rebellion: Climate change protesters block London bridges epa07173093 A pro environment protester infornt of police on Lambeth bridge in London, Britain, 17 November 2018. Reports state that the protest organized by Extinction Rebellion group is planning to close five main bridges across the river Thames, seeking to bring attention to political inaction on issues of pollution and climate change. EPA/FACUNDO ARRIZABALAGA FACUNDO ARRIZABALAGA EPA Extinction rebellion: Climate change protesters block London bridges epa07172601 Pro environment protesters block Westminster bridge in central London, Britain, 17 November 2018. Reports state that the protest organized by Extinction Rebellion group is planning to close five main bridges across the river Thames, seeking to bring attention to political inaction on issues of pollution and climate change. EPA/FACUNDO ARRIZABALAGA FACUNDO ARRIZABALAGA EPA Extinction rebellion: Climate change protesters block London bridges epa07172698 Pro environment protesters hold a placard as they block Westminster bridge in central London, Britain, 17 November 2018. Reports state that the protest organized by Extinction Rebellion group is planning to close five main bridges across the river Thames, seeking to bring attention to political inaction on issues of pollution and climate change. EPA/FACUNDO ARRIZABALAGA FACUNDO ARRIZABALAGA EPA Extinction rebellion: Climate change protesters block London bridges Demonstrators on Westminster Bridge in London for a protest called by Extinction Rebellion to raise awareness of the dangers posed by climate change. PRESS ASSOCIATION Photo. Picture date: Saturday November 17, 2018. See PA story PROTEST Rebellion. Photo credit should read: John Stillwell/PA Wire John Stillwell PA Extinction rebellion: Climate change protesters block London bridges Environmental campaigners from the direct action group Rebellion demonstrate on Westminster Bridge in central London, Britain, November 17, 2018. REUTERS/Peter Nicholls PETER NICHOLLS Reuters Extinction rebellion: Climate change protesters block London bridges epa07172703 Pro environment protesters hold a placard as they block Westminster bridge in central London, Britain, 17 November 2018. Reports state that the protest organized by Extinction Rebellion group is planning to close five main bridges across the river Thames, seeking to bring attention to political inaction on issues of pollution and climate change. EPA/FACUNDO ARRIZABALAGA FACUNDO ARRIZABALAGA EPA Extinction rebellion: Climate change protesters block London bridges Demonstrators take part in a pro-environment protest as they block Westminster Bridge in central London on November 17, 2018, to show anger at government inaction on climate and ecological issues. - Organized by Extinction Rebellion, the protest is part of many taking place this weekend to bring attention to political inaction on issues of pollution and climate change. (Photo by Tolga AKMEN / AFP)TOLGA AKMEN/AFP/Getty Images TOLGA AKMEN AFP/Getty Extinction rebellion: Climate change protesters block London bridges epa07172629 Pro environment protester holds a placard as they block Westminster bridge in central London, Britain, 17 November 2018. Reports state that the protest organized by Extinction Rebellion group is planning to close five main bridges across the river Thames, seeking to bring attention to political inaction on issues of pollution and climate change. EPA/FACUNDO ARRIZABALAGA FACUNDO ARRIZABALAGA EPA Extinction rebellion: Climate change protesters block London bridges Environmental campaigners from the direct action group Rebellion demonstrate on Westminster Bridge in central London, Britain, November 17, 2018. REUTERS/Peter Nicholls PETER NICHOLLS Reuters

“We have tried marching, and lobbying, and signing petitions,” Ms Jacout added. “Nothing has brought about the change that is needed. And no damage that we incur can compare to the criminal inaction of the UK government in the face of climate and ecological breakdown.”

Writer George Monbiot joined the protest at Blackfriars bridge. “Something I have been waiting for, for a very long time is happening,” he said.

“People are risking their liberty in defence of the living world in very large numbers. It is only when we are prepared to take such action that people begin to recognise the seriousness of our existential crisis.”

Extinction Rebellion said 50 people were arrested following several actions staged in London earlier this week, including the spray-painting of walls surrounding the House of Parliament.

Others chained themselves together and glued their hands to the entrance of the Department of Energy.

Activists also unveiled a banner that read “We’re f****d” over Westminster Bridge.

The group wants the UK government to commit to net zero carbon emissions by 2025 and reverse policies inconsistent with addressing climate change.

Campaigners are also demanding a “citizen’s assembly” to be set up to allow ordinary people a voice in creating new environmental policies.

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Dozens of major countries are pursuing environmental policies that would lead to temperature rises exceeding 5C by the end of the century, according to a new study by Australian and European researchers.

Last month a landmark UN report warned that greenhouse gas emissions must be cut almost in half by 2030 to avert global environmental catastrophe.