Insulate Britain protest cost GMP at least £10,000
The group targeted a major road near Manchester Airport earlier this year
Policing Insulate Britain's road-blocking protests cost taxpayers at least £4.3 million, an investigation has found.
Transport Secretary Grant Shapps said he was "appalled" by the bill, which was disclosed by police forces in response to Freedom of Information requests by the PA news agency.
The Metropolitan Police said it spent £4 million dealing with the climate group's stunts between September 13 and November 20.
Some 6,651 of the force's officers and staff were involved, at a cost of £3.1 million.
A further £600,000 was spent on deploying vehicles, while the overtime cost was £300,000.
Greater Manchester Police provided a figure totaling £10,000, but only included overtime bills meaning the actual cost of policing protests in their area was considerably higher.
Insulate Britain, an offshoot of Extinction Rebellion, wants the Government to insulate all UK homes by 2030 to cut carbon emissions.
It repeatedly blocked major roads between September and November, causing long traffic jams.
Activists often glued their hands to the road or each other to make it harder to remove them.
The group frequently targeted the M25, the UK's busiest motorway, but also blocked a major route near Manchester Airport in November.
At one stage police officers were deployed at every junction of the M25 in an attempt to stop the group.
Shapps: 'I am appalled'
Mr Shapps told PA: "I am appalled at the amount of time and public money that's been spent policing the selfish actions of Insulate Britain.
"Not only did their guerrilla tactics wreak havoc on our roads and inflict misery to thousands of motorists, but they diverted our emergency services away from vital work, costing the UK taxpayer millions in the process."
Ken Marsh, chairman of the Metropolitan Police Federation, which represents rank and file officers, described the cost of policing the protests as "staggering".
He said: "Unfortunately we have to police what's put in front of us.
"It's disgusting that we're having to spend that sort of money on these protests."
Mr Marsh described responding to the demonstrations on 70mph motorways as "some of the most dangerous things my colleagues have had to do".
Police made hundreds of arrests, but many suspects returned to the roads just hours after being released from custody.
This led to Government-owned National Highways applying to the High Court for injunctions to ban protests on motorways and major A roads in England.
Insulate Britain spokeswoman Tracey Mallaghan said the group would "much rather money was being spent on insulating homes and helping get people out of fuel poverty".
But she believes their actions have made home insulation "something people are talking about".
Asked why they blocked roads rather than conducted legal protests, she replied: "When we went to Parliament as Insulate Britain, that just didn't get the same amount of (media) coverage.
"It seems the only way we can get air time is by annoying enough ordinary people."
She added: "I just can't look my children in the face and say 'this problem is too big, we're not going to do anything'.
"Our Government has proved time and time again they're not doing what is necessary for our children, for the future. So how can we stop?"