British energy firm Cuadrilla scaled back its operations at a rural site in southern England on Friday as more than 1,000 protesters prepare a six-day "action camp" in protest against fracking.

The company, which specialises in hydraulic fracturing for shale gas, the controversial technique known as fracking, will reduce exploratory drilling at Balcombe in West Sussex due to concerns over the protest by "No Dash For Gas" campaigners.

Cuadrilla said it intended to resume full operations "as soon as it is safe to do so".

Demonstrators declared victory, but insisted they would not give up their campaign.

One activist at the Balcombe site, Luke Johnson, said: "Cuadrilla's announcement that they'll halt drilling is already a victory for us, but it's only a start. We would like to make sure they don't frack in Balcombe, or anywhere else at all."

Cuadrilla said in a statement: "After taking advice from Sussex Police, Cuadrilla is scaling back operations ahead of this weekend's 'No Dash for Gas' event.

"During this time, our main concern is the safety of our staff, Balcombe's residents and the protesters following threats of direct action against the exploration site.

"We will resume full operations as soon as it is safe to do so."

Fracking has unlocked an energy boom in the United States, but has been banned in other countries over fears of environmental damage.

Protesters have been camped at the site for weeks, but organisers say they are set to be reinforced by up to 1,000 more campaigners for the six-day Reclaim the Power Camp.

The site has been secured with barbed wire fences but the threat of confrontation remains after the anti-fracking campaign group promised "direct action".

Police have made about 40 arrests since the demonstrations began three weeks ago.

Campaigners were erecting marquees, tents and kitchen and toilet facilities on the site, which is about a mile from the exploratory drilling project.

Celebrities including the daughter of Pretenders' singer Chrissie Hynde and Kinks frontman Ray Davies have demonstrated at Balcombe, not always to the delight of local residents who have accused them of hijacking the protest.

Although Cuadrilla has not yet started fracking, some fear the company will use the technique after it has completed exploratory drilling, which began at the site on August 2.

Prime Minister David Cameron said last week Britain would be making a "big mistake" if it shunned shale gas extraction.

His government believes fracking could increase Britain's energy security, create thousands of jobs and boost tax revenues.

But other countries are unconvinced -- French President Francois Hollande, for example, has ruled out shale gas exploration during his term in office.

Fracking involves using injecting huge amounts of pressurised water mixed with chemicals into a well to crack open shale, the sedimentary rock containing hydrocarbons, to release natural gas.

Environmentalists have warned that chemical-laced waste could contaminate fresh water resources, while many believe fracking causes minor earthquakes.

Cameron has dismissed the concerns, insisting that "there is no question of having earthquakes and fire coming out of taps and all the rest of it".