Parliament's only Green MP, Caroline Lucas, has been arrested at an anti-fracking demonstration in Balcombe.
The former party leader was part of a group of protestors conducting a sit-in against energy firm Cuadrilla, which is exploring the feasibility of drilling for oil in the area.
Eyewitnesses said the Green MP looked shaken after her son was rushed away by police but that she remained at the sit-in. Later it was reported that she was arrested.
"They've stopped their exploratory drilling but as soon as we've gone they'll start again," Lucas told the BBC earlier.
"This isn't just about Balcombe, important though that is, it's about a whole new government policy to do with getting more and more fossil fuels out of the ground.
"The government is not listening so I think there are times when peaceful direct action can be legitimate."
The police served a Public Order Act notice earlier, which allows them to take action if they believe a crowd could cause serious damage to property or disrupt the life of the community.
Demonstrators had blocked the B2036 between Balcombe and Cuckfield as part of a day of action which caused Cuadrilla to temporarily close the drilling programme.
Campaigners also forced their way into the company's Staffordshire headquarters and others glued themselves to the London office of Bell Pottinger, which does the firm's PR.