A 2.1-magnitude tremor has been reported at the UK’s only active fracking site – days after a 1.55-magnitude movement.

Saturday night’s “micro seismic event” at the Cuadrilla site near Blackpool is believed to be the largest ever fracking-related tremor in the UK.

The company said the tremors, detected at 11: 01 p.m., lasted about one second and occurred when there was no hydraulic fracturing.

A spokeswoman for the company said: “Minor ground movements of this level are to be expected.

“While this event has been felt by people on our site and some local households, it is well below anything that could cause harm or damage to anyone or their property.”

Under UK rules, work must be suspended for 18 hours if seismic activity of magnitude greater than 0.5 is detected.

Cuadrilla has previously described the limit as” extremely low ” and wants a review of the rules, which are much tougher than in the US.

According to the British geological survey, the tremors were 1.2 miles deep and were felt by residents in areas such as great Plumpton, Blackpool and Lytham St Annes.

Cuadrilla claims on Wednesday the tremor would have felt like someone dropping a large shopping bag on the floor.

Fracking, or hydraulic fracturing, involves injecting water and chemicals at high pressure to break up rock and extract gas.

However, it can cause tremors and is opposed by environmentalists who say it pollutes drinking water, pollutes air and water and contributes to climate change.

There have been regular protests on the Lancashire site.

Cuadrilla says fracking work will be completed by the end of November, followed by a stream of well testing, with results expected in early 2020.

He hopes that research tests will show the potential of shale gas for the UK and estimates about 1,300 trillion cubic feet of gas is contained in the area.

The government says shale gas could be an important new domestic energy source, reducing dependence on imports as well as bringing economic benefits.