Green MP Caroline Lucas arrested at climate protest
Green MP Caroline Lucas and her son were among protesters arrested at a site in West Sussex where energy firm Cuadrilla is drilling for oil.
Police dispersed hundreds of anti-fracking demonstrators who blocked the B2036 between Balcombe and Cuckfield.
Officers served a Public Order Act notice, saying the crowd might cause serious damage to property or disrupt the life of the community.
Cuadrilla said it condemned all illegal direct action against its operations.
About 30 people have been arrested at the Balcombe site, Sussex Police said.
Earlier, campaigners forced their way into the company's headquarters in Lichfield, Staffordshire.
Six activists also glued themselves to the London HQ of Bell Pottinger, Cuadrilla's PR company.
Cuadrilla has suspended operations at Balcombe after Reclaim the Power activists set up a six-day camp near the site.
'Dignity and respect'
Reclaim the Power said four activists used locks and glue to attach themselves to another activist's wheelchair outside the main gate at Balcombe, while others blocked the road.
The campaigners said police "charged, shoved and kettled" a group including children, people in wheelchairs, pensioners and Green MP Mrs Lucas, whose Brighton Pavilion constituency is about 20 miles away.
"This is an outrageously aggressive response to a day of principled civil disobedience," said protester Ewa Jasiewicz.
"All our actions have safety, dignity and respect at their core.
"Cuadrilla and the government were desperate to discredit fracking opponents. We offered them no aggression so they are creating it themselves."
No Dash for Gas said it had lodged a formal complaint with Sussex Police, claiming an officer was not wearing his ID number while carrying out an arrest.
Amy Scott, from the campaign group, said: "The tactics and force used was completely disproportionate to the calm and friendly situation."
Sussex Police posted on Twitter: "Aware of video showing officer without epaulette. Appears to be loose like it has fallen off/been pulled off. We will look into this.
"Epaulettes are removable so officers can clip them onto a clean top/shirt/tunic each time."
Earlier Sussex Police posted on Twitter: "We would like to reiterate that protesters aren't being kettled and are free to leave the site as they wish."
A spokesman said: "Police moved in to clear a large group of people in front of an emergency access to the Cuadrilla drilling site."
Supt Lawrence Hobbs said: "We are more than happy to facilitate peaceful protest, but those who are intent on criminal action will be arrested."
The road through the village has been cleared of protesters, the BBC's James Pearce reported.
Ms Lucas, who had been sitting with the protesters, said earlier she was prepared to be arrested.
After being detained by police, she said: "People today, myself included, took peaceful non-violent direct action only after exhausting every other means of protest available to us.
"I'm in the privileged position of being able to put questions to the government directly and arrange debates in parliament, but still ministers have refused to listen.
"Despite the opposition to fracking being abundantly clear, the government has completely ignored the views of those they are supposed to represent.
"When the democratic deficit is so enormous, people are left with very little option but to take peaceful, non-violent direct action."
Tom Harris, Labour MP for Glasgow South, criticised Ms Lucas on Twitter, saying she "was always going to get arrested - that was the only point of her being there. Pure self-promotion."
About 20 protesters also demonstrated outside the constituency office of Horsham's Conservative MP Francis Maude.
A spokeswoman said they targeted the office of Mr Maude - in whose constituency Balcombe is situated - because "he refuses to listen to the concerns of the local people and stand up for their right not have their country destroyed by fracking".
The campaigners fear the oil drilling will be followed by fracking - or hydraulic fracturing - a technique designed to recover gas and oil from shale rock.
No Dash for Gas said activists entered Cuadrilla's Lichfield building and banners were hung outside. Banners were also unfurled at Bell Pottinger's offices.
Six people have been arrested in central London for aggravated trespass. Two were also held on suspicion of criminal damage, said City of London Police.
Cuadrilla and Bell Pottinger said their offices remained open and business was carrying on as usual.
"We condemn all illegal direct actions against our people and operations," Cuadrilla said in a statement.
The firm insisted the morale of its staff at various sites was "fine" and they and the teams supporting the company were "doing a magnificent job".
"They know that what we are doing is legal, approved and safe, and that shale gas is essential to improve our energy security, heat our homes, and create jobs and growth.
"Cuadrilla is rightly held accountable for complying with multiple planning and environmental permits and conditions, which we have met and will continue to meet.
"Clearly we are held to one set of legally enforceable standards while some protesters believe that they can set out and follow their own."