Environmental protesters claim they cycled past security staff before forcing their way into Didcot Power Station early this morning.

More than 20 protesters broke into Didcot A — the coal-fired power station — at about 5am and are currently occupying the tall chimney and a coal conveyor.

In the past hour, five police vans have arrived at the site, and there about 40 police officers standing by.

The protesters met at the Camp for Climate Action in Blackheath, London, earlier this year.

Nine members climbed the steps of one of the chimneys and said they will stay at the power station, run by RWE npower, for "as long as possible".

A further 13 are on the station's coal conveyer.

Speaking from the chimney, Joanna Bates, 21, from Leeds, told the Oxford Mail: “A group of us cycled past the security guard at about 5am and he couldn’t stop us — we were too quick for him.

“We then used an angle grinder to cut down the gates to get to the chimney.

“People have come from across the country for this demonstration and we have enough food, clothes and water for a week.

“We know we are going to get arrested but we think this is a very important issue.”

Protester Amy Johnson, a 20-year-old student from Oxford, added: "RWE npower have become at the forefront of trying to push for more coal, and want to build 30 more coal-fired power stations. We're here to tell them that can't possibly happen.

"We're planning on staying as long as possible.”

Sunita Patel, a spokesman for RWE npower, said: “We can confirm that approximately 20 people entered Didcot A Power Station by forced entry, some time before 5.30am this morning. At this stage, power generation is not affected.

“We are co-operating closely with the police and our priority remains the health and safety of staff and also protesters.”

The break-in follows a similar incident on November 3, in 2006 when 25 Greenpeace protesters broke into Didcot A.

They occupied part of the power station and painted “Blair’s Legacy” down the main 650ft stack, before surrendering to police.

The demonstration cost RWE npower an estimated £690,000 by disrupting power generation at the coal-fired Didcot A part of the plant.

The Greenpeace campaigners were later fined almost £5,000.

Chief Supt Brendan O’Dowda, Oxfordshire area commander, said: “Police are working in partnership with site authorities to resolve the situation.”

RWE npower’s Didcot facility is host to two power stations — the 2,000 MW dual-fired A station and the 1,360 MW combined cycle gas turbine B station.