Protesters have climbed motorway signs on the M25 in response to the extreme temperatures in the UK and what they describe as the Government’s “inadequate preparations” for climate change.

Five demonstrators scaled gantries which support overhead motorway signs in three places on the M25, causing police to close sections of the road.

Protesters climbed signs at junction 10 eastbound near Cobham, Surrey, the Poyle interchange at Heathrow between junctions 14 and 15, and in Dartford between the Queen Elizabeth Bridge northbound and junction 30.

Bus driver Ashley Reid takes special needs children aged seven to 10 to a school in Leatherhead by travelling between junction 12 and 10 and said his pupils, who start at 9.15am, were around 90 minutes late for their last day of term as a result of the disruption.

“We joined (the motorway) just after 9am and we didn’t arrive at school until 10.45am… with their autism (they) found it difficult to understand and stay calm,” the 40-year-old, from Reigate, told the PA news agency.

“It was really disruptive and I felt so sorry for them… today was their last day before the summer break and they would all be changing classes so they just wanted to get to school and spend time with their teachers and friends.”

The children are set to finish school at 1pm, when Mr Reid will have to return to the school to pick them up.

“I am sympathetic to the cause that these people are protesting against; however, they are disrupting a lot of innocent motorists and (in my opinion) will lose more sympathy than they gain,” he added.

A travel alert from Highways England on Twitter warned: “There are delays of over an hour on the M25 anti-clockwise in Surrey due to an ongoing Surrey Police led incident within J10 (for A3, Guildford). 3 lanes (of 4) are currently closed.

“If this incident impacts on your planned route, please allow extra journey time as there is over nine miles of congestion on approach. Plan ahead, you may wish to re-route or even delay your journey.”

A further Highways alert was issued for Berkshire, which said: “The M25 in Berkshire is closed clockwise between J14 (for Heathrow Airport) and J15 (for the M4) due to an ongoing Metropolitan Police led incident.

“National Highways Traffic Officers are providing assistance with traffic management on scene.”

Surrey Police said: “Officers are dealing with a protester on a gantry on the M25 just past junction 10 of the anti-clockwise carriageway this morning (20 July), and three lanes are currently closed.

“We hope to have the area cleared as soon as possible and will keep you informed of further updates via our social media channels. In the meantime motorists should avoid the area.”

Essex Police also announced a further M25 closure on Twitter. “The M25 in Thurrock between J30 and J31 has been closed while we respond to reports of people on the gantry above the road.

“We’re working to resolve the incident as quickly and safely as possible but please avoid the area.

“We appreciate your patience and understanding.”

The environmental protest group has said more groups are on their way, as part of planned action between Wednesday and Friday.

A spokesman for Just Stop Oil said: “The main thing is, we’ve just seen 40 degree temperatures, which have been predicted for decades, maybe it’s happening a bit faster. But it has just revealed how inadequate the Government’s preparations for climate change are and their entire policy, and basically we’re just saying it’s evident now we cannot continue.

“As we’re going on, we need to stop new oil. It’s the first step to ensuring we have a liveable future, and maybe it’s already too late.

“This is something we definitely need to do.”

The group chose the M25 as the site of the action as it is “the place where we confront the carbon economy headlong and bring our resistance into full public view. The M25 has a kind of iconic status as the motorway from hell, doesn’t it? So it’s a reference to that”.

Temperatures reached 40C in the UK for the first time ever on Tuesday, which led to major incidents announced by fire brigades in London, Leicestershire and South Yorkshire as fires broke out across the country in the heat.

The group is demanding that the Government make a “meaningful statement” that it will commit to stop licensing and consents for the exploration, development and production of fossil fuels in the UK, which it says is “the necessary first step to ensuring a liveable future”.

It added that it plans to hold further actions against oil infrastructure in coalition with trade unions, environmental groups and civil society organisations in the coming months.

A spokesperson for the National Police Chiefs’ Council said: “The ability to protest peacefully in a democracy is important and where lawful, forces will seek to facilitate protests – but even if a protest is peaceful and non-violent, this doesn’t always mean the actions taken by protestors are legal.

“We are concerned by the fact protestors are taking significant risks to their own safety and to the safety of others on the roads. Forces are working together, sharing information, and will take action against anyone acting illegally.

“We fully understand that disruptive activity will have a negative impact on members of the public who are trying to get on with their day. Our aim is to work closely with Highways England and other partners to minimise disruption as quickly as possible and ensure the flow of traffic can continue safely.

“At a time of significant demand on emergency services, if officers are on the roads resolving this disruption they aren’t available elsewhere preventing crime and keeping the public safe.”