Insulate Britain have blocked three three major routes into London, including Hanger Lane and Arnos Grove alongside the Blackwall Tunnel.
Protesters from Insulate Britain blocked the Blackwall Tunnel, a significant artery, linking north and south of the river, during rush hour on Monday morning causing large queues.
It is the latest in a string of protests from the group, which has previously targeted the M25, M4 and Port of Dover.
The group said around 50 people were involved in the demonstration.
Later, the home secretary, Priti Patel, will warn that protesters who block the highway could face unlimited fines and up to six months in jail.
Police are also to be given the powers to stop and search activists for “lock-on” equipment used to prevent them from being moved.
The group has pledged to continue its actions until the government makes “a meaningful statement indicating that they will insulate all of Britain’s 29 million leaky homes by 2030”. The group said in a statement: “It’s incomprehensible that the government is continuing to delay action on home insulation when we urgently need to cut our carbon emissions, eliminate fuel poverty and help hard-working families with their rising energy bills. “Added to which industry is crying out for the government to show some leadership and get behind a national retrofitting strategy. Come on Boris: get on with the job.”