
Four campaigners have been arrested ahead of a "mass day of action" against carbon emissions at Britain's largest coal-fired power station.
Hundreds of demonstrators plan to disrupt operations at Drax Power Station in North Yorkshire on Thursday.
Two people were arrested on suspicion of carrying a weapon and two were held after being found in the Drax premises.
"This is a sad contrast to the sincere and law abiding intentions of the majority", police said.
North Yorkshire Police's Deputy Chief Constable Ian McPherson said protesters had not told police of their plans for Thursday's action.
He said: "We have a number of individuals who joined us in North Yorkshire who largely are behaving themselves.
"However we are conscious that within that group there is a hardcore - a number of individuals who have made their aims very clear, see themselves as rising above the law and it's those individuals who I think will undermine what is a serious point."
A spokeswoman for the protesters said their actions would involve marches, blockades and attempts to get into the site.
Michelle Bernstein, 28, from York, said: "Many of us are prepared to break the law, because the powers-that-be are addicted to planet-trashing economic growth.
"Shutting down a power station isn't enough to stop climate change but it's a start."
About 600 people are staying at the Camp for Climate Action, next to the power station.
Some of them have undertaken "civil disobedience training" at the site and plan to shut down the power station, near Selby.
Drax is the biggest coal-fired power station in Europe, more than twice as big as any other power station in the UK.
Protesters claim it is obsolete and should be closed down and replaced with cleaner forms of power.
North Yorkshire police officers and staff from other forces will be at the power station site and the camp on Thursday "to ensure that residents, power station employees and the demonstrators themselves do not come to harm, and that no laws are broken".
Drax Power successfully applied for an injunction earlier this month banning unauthorised people from entering the site or using an adjacent footpath.
The injunction, to last indefinitely, was brought because Drax said it did not want protesters to be harmed by the complex industrial processes at the plant.
It also sought the injunction because it said Drax was an "important national strategic asset", contributing 7% of the country's electricity.