Police made at least 38 arrests today as hundreds of eco-warriors marched on Britain's biggest coal-fired power station in a bid to disrupt operations.

The protesters were aiming to force a temporary closure at the plant, complaining that it spews out almost 21 million tonnes of carbon dioxide a year.

Chief Inspector Barry Smith of North Yorkshire Police said that the majority of the activists were arrested outside the perimeter of the Drax power station, near Selby in North Yorkshire, but conceded that "a small number" had gained access to the site.

He said that the protesters were arrested for offences ranging from possession of offensive weapons to causing a public nuisance and criminal damage. He told reporters near the power station that a number of protesters had managed to climb a lighting tower this morning, but had since been taken down and arrested.

Mr Smith said: "There was no disruption whatsoever to the functioning of the power station at all. There are no protesters inside the power station itself. There are a number on land adjacent to the power station."

But a spokesman for the demonstrators, Conor O'Brien, disputed the police version of events. He said all 28 of those arrested had breached the perimeter of the power station and added that one of those who climbed up the lighting tower was still there and planned to remain.

Mr O'Brien told Times Online that it was still possible that the demonstrators would penetrate the Drax plant itself. "The power station has weak points and although it's well guarded people can actually get in fairly easily," he said.

The demonstrators set up their Camp for Climate Action about two miles from Drax at the weekend and began several days of 'civil disobedience training' before today's day of "creative mass action" against the UK’s biggest single emitter of carbon dioxide.

Mr Smith said that seven forces had helped to staff the police operation and he warned demonstrators that no criminal acts would be tolerated.

He said that there were fewer demonstrators than the force had anticipated. Officers had been told there would be around 2,000 people, but estimated that around 600 were there today.

At about 9.05am, hundreds of demonstrators left the site close to the village of Barlow led by a group of small children and parents with pushchairs.

As they made their way up the small lane to the main road, they were joined by another large group of demonstrators dressed in white overalls and with their faces covered.

As they reached the top of the lane where dozens of police vans were parked, a single line of police blocked their way, apparently trying to prevent them entering the village of Barlow.

A large group then moved off down a farm track in the opposite direction while a smaller group remonstrated with the officers. There were a few minor scuffles as police attempted to stop demonstrators skirting around their line.

Once the bulk of protesters had moved off across the field, apparently in the opposite direction from the giant power station, about 50 campers remained dancing, playing loud music and chatting.

Police roadblocks were set up along all the main routes to the plant, causing long tailbacks for commuters. Dozens of police vans have been strategically placed around the area.

In one layby, ten vans from the Metropolitan Police were seen parked, and on the main Selby road 25 police Transit vans were spotted in convoy. Fencing has also been put up across the railway lines skirting the plant.

A North Yorkshire Police spokesman said officers were in place in an attempt to "facilitate any peaceful demonstrations and deal firmly with anyone who steps outside the law".

Explore UK News

• Crime News

• Education News

• Health News

• Scotland News

Times Recommends

• A vicar’s wife: ‘There is no one to fight for us’
• Every little helps at the supermarket
• Ugg or Fitflop? The battle of the boots