Two more arrests have been made by police investigating protests which blocked the M25 five times in the past two weeks.
They were both arrested on suspicion of conspiracy to cause public nuisance.
Three arrests were made for the same offence last week.
Some 28 arrests have been made for obstructing the public highway, the force added.
Those arrested have been released under investigation.
The protests have been carried out by supporters of Insulate Britain, which wants the Government to insulate and retrofit homes across the UK to cut climate emissions.
London Mayor Sadiq Khan said he “passionately believes in the right to protest peacefully, lawfully, safely” but it is “completely wrong” to target the M25 because “it’s not safe”.
Speaking to reporters after a speech on the climate and air pollution crises facing London and the world, Mr Khan said: “You’re endangering the lives of those on the M25, they could be people rushing to get to a hospital, it could be they’re going to an appointment, and you’re jeopardising their safety by jumping in front of cars on the M25.”
And he warned: “You’re not encouraging people to join our cause, you’re not encouraging people to understand the importance of addressing the climate emergency.”
Mr Khan said he had been investing in insulation and retrofitting in London and had been lobbying the Government to give the capital more help to do so.
But he warned: “You’re not making people like me more sympathetic to this issue of climate emergency, and actually what you’ve done inadvertently is to get parliamentarians bringing in laws to reduce the ability of those of us who want to protest lawfully, peacefully and safely.
Commons Leader Jacob Rees-Mogg has also criticised the protesters on UK roads as “frightful old humbugs, causing trouble, distress, inconvenience and nearly causing people to die”.
The Government has successfully applied to the High Court for an order which prohibits anyone from blocking the M25, with those breaking the injunction facing a possible two years in prison or an unlimited fine.