Climate group Insulate Britain says it will suspend its road-blocking protests for the next 11 days.
The organisation – which has caused misery for drivers with protesters sitting on the M25 motorway and other major roads – said it will stop its "campaign of civil resistance" until October 25.
In a letter to Boris Johnson, the group wrote: "Insulate Britain would like to take this opportunity to profoundly acknowledge the disruption caused over the past five weeks.
"We cannot imagine undertaking such acts in normal circumstances. But the dire reality of our situation has to be faced.
"We invite you to make a meaningful statement that we can trust... that your government will take the lead needed to insulate and retrofit our homes."
Transport Secretary Grant Shapps said: "Sitting on roads and preventing everyone else from going about their lawful business is downright dangerous and counterproductive.
"Rather than apologising to the motorist now and returning in a week-and-a-half, they must call off their reckless campaign forever."
Insulate Britain – an offshoot of Extinction Rebellion – wants the UK government to insulate all UK homes by 2030 to cut carbon emissions.
It has blocked roads on 14 days over the past five weeks, with activists often gluing their hands to the carriageway to increase the length of time it takes for police to remove them.
Hundreds of arrests were made, with some people detained several times.
Angry drivers often confronted the protesters and attempted to drag them away.
The latest demonstration was near a busy industrial estate in Thurrock, Essex, on Wednesday morning.
Insulate Britain previously admitted its actions on the M25 were "in breach" of an injunction obtained by the government last month.
People who break injunctions can be found to be in contempt of court, but the protests continued as prosecutions usually take several months.
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