Ms Lucas said she would prefer direct action “closer” to people in power, such as in Downing Street or at the Treasury.
But she refused to criticise the protesters, saying: “In extreme situations, it’s reasonable to take extreme actions – and that is what has driven these protesters to do that.”
The former Green party leader was quizzed amid expectations that a radical new protest group – an offshoot of Extinction Rebellion – will target Britain’s motorways for many weeks.
Insulate Britain is thought to want to send dozens of its activists to prison to coincide with the Cop26 summit in Glasgow – and those arrested for occupying the M25 went back to block it again straight after release.
Asked if she would join the protests if invited, Ms Lucas told Sky News: “I fully understand why protesters have felt driven to something more dramatic”, accusing ministers of “ignoring” less disruptive protests.
“We face an existential crisis and emergency and we need to take emergency action,” she said.
Ms Lucas also attacked the government’s priorities by antagonising China with the AUKUS military alliance, when Beijing’s cooperation to make Cop26 a success is essential.
Xi Jinping, the Chinese premier has yet to say he will travel to Glasgow – and Alok Sharma, the Cop26 president – has admitted frustration at a lack of “detailed plans” from the world’s biggest CO2 emitter.
“Efforts at international diplomacy are being entirely undermined by government actions at home,” she warned.
“The first rule of diplomacy is to walk your talk and yet, both on the finance for climate and on the emissions reductions, this government is doing the opposite.”
Asked if a deal to tackle the climate emergency can be struck without China, she added: “I think that’s almost impossible to envisage, no.
“It is absolutely essential that China is there and that’s why I am deeply concerned about this new so-called AUKUS deal because we have just enraged the Chinese even more.
“If Cop26, these UN climate talks, are our top diplomatic priority then everything else should be taking second place to that – so I’m deeply worried about relations with China.”
Mr Sharma agreed Beijing’s role in Glasgow is crucial, saying only: “I am very, very hopeful that we will have a delegation from China.”
He told Sky News: “There is no doubt that China is going to be part of the key to all of this. They are the biggest emitter in the world.
“They have said to me they want the Cop26 to be a success. The ball is in their court. We want them to come forward and make it a success together with the rest of the world.”
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