Environmental campaigners planning on grounding flights at Britain's busiest airport risk "long jail sentences", police have warned.

Heathrow Pause activists - a splinter of the Extinction Rebellion movement but separate from them - have said they will operate small toy drones near the transport hub from 3am on Friday 13 September.

A spokesman for the group said they expect "somewhere between 50 to a couple of hundred people" to be involved in the action, with each person using a drone.

London's Metropolitan Police have promised they will do "everything in its power to prevent and stop any such criminal activity".

Deputy Assistant Commissioner Laurence Taylor said: "Heathrow Airport is part of our national infrastructure and we will not allow the illegal activity of protesters to cause misery to thousands of air travellers. The dangers of flying drones in airspace used by airliners carrying passengers are stark and the consequences potentially very severe.

Extinction Rebellion protesters block roads in five cities Show all 22 1 /22 Extinction Rebellion protesters block roads in five cities Extinction Rebellion protesters block roads in five cities Demonstrators from the Extinction Rebellion climate environmental activist group protest outside of The Royal Courts of Justice on The Strand in central London AFP/Getty Images Extinction Rebellion protesters block roads in five cities Extinction Rebellion demonstrators with a green boat in Cardiff PA Extinction Rebellion protesters block roads in five cities Environmental campaigners take part in a road blockade climate change protest organised by the group Extinction Rebellion in Leeds city centre, West Yorkshire Dan Rowlands / SWNS.com Extinction Rebellion protesters block roads in five cities Extinction Rebellion protesters occupy Bristol Bridge as part of a "Summer Uprising" in Bristol SWNS Extinction Rebellion protesters block roads in five cities Extinction Rebellion Scotland hold a protest on Trongate, Glasgow SWNS Extinction Rebellion protesters block roads in five cities Activists block roads near the Tron Clock tower in Glasgow Getty Images Extinction Rebellion protesters block roads in five cities Police speak with an Extinction Rebellion protester sitting on a boat they have parked outside the Royal Courts of Justice in London PA Extinction Rebellion protesters block roads in five cities Extinction Rebellion Activists block roads near the Tron Clock tower in Glasgow Getty Images Extinction Rebellion protesters block roads in five cities Activists block roads near the Tron Clock tower in Glasgow Getty Images Extinction Rebellion protesters block roads in five cities Protesters occupy Bristol Bridge in Bristol SWNS Extinction Rebellion protesters block roads in five cities Protesters from Extinction Rebellion outside the Royal Courts of Justice in London PA Extinction Rebellion protesters block roads in five cities Protesters from Extinction Rebellion outside the Royal Courts of Justice in London PA Extinction Rebellion protesters block roads in five cities Protests outside of The Royal Courts of Justice AFP/Getty Images Extinction Rebellion protesters block roads in five cities Police officers walk stand in front of a blue boat belonging to Extinction Rebellion protesters outside the Royal Courts of Justice EPA Extinction Rebellion protesters block roads in five cities Protesters from Extinction Rebellion in Leeds PA Extinction Rebellion protesters block roads in five cities Protesters from Extinction Rebellion in Leeds PA Extinction Rebellion protesters block roads in five cities Demonstrators listen to speakers as they protest outside of The Royal Courts of Justice AFP/Getty Images Extinction Rebellion protesters block roads in five cities Environmental campaigners take part in a road blockade climate change protest organised by the group Extinction Rebellion in Leeds city centre Dan Rowlands / SWNS.com Extinction Rebellion protesters block roads in five cities Environmental campaigners take part in a road blockade climate change protest organised by the group Extinction Rebellion in Leeds city centre, West Yorkshire Dan Rowlands / SWNS.com Extinction Rebellion protesters block roads in five cities Environmental campaigners take part in a road blockade climate change protest organised by the group Extinction Rebellion in Leeds city centre, West Yorkshire Dan Rowlands / SWNS.com Extinction Rebellion protesters block roads in five cities Environmental campaigners take part in a road blockade climate change protest organised by the group Extinction Rebellion in Leeds city centre Dan Rowlands / SWNS.com Extinction Rebellion protesters block roads in five cities Environmental campaigners take part in a road blockade climate change protest organised by the group Extinction Rebellion in Leeds city centre Dan Rowlands / SWNS.com

"We would urge anybody intending to join this event with a view to committing criminal activity, whether considered peaceful or not, to think twice. Protesters should note that endangering the safety of an aircraft is a very serious offence that can result in a long jail sentence."

Heathrow Pause said their plans to fly the machines within the 5km zone surrounding the airport are "exploiting a loophole in Heathrow Airport's health and safety protocol".

They added: "Drones will not be flown in flight paths and there will be no risk of harm to anyone. We know that we will be arrested. We know that we face significant prison sentences for our actions. We have lives, we have families, we do not wish to go to prison. But we are steadfast in our resolve. We do this in defence of life. We do it because our consciences leave us no other choice but to act."

The activists said they will meet with police and airport authorities to discuss their plans later this week.

A Heathrow spokesman said: "We agree with the need to act on climate change. This is a global issue that requires constructive engagement and action. Committing criminal offences and disrupting passengers is counter-productive. Flying of any form of drone near Heathrow is illegal and any persons found doing so will be subject to the full force of the law.

"We are working closely with the Met Police and will use our own drone detection capability to mitigate the operational impact of any illegal use of drones near the airport."