A former RAF pilot has questioned whether using military resources to patrol the English Channel to spot migrant crossings is “sensible”.

A plane was dispatched to survey the Channel on Monday after the flight was authorised by Defence Secretary Ben Wallace following the Home Office’s formal request for help from the Ministry of Defence (MoD).

The Atlas A400M transport aircraft, which is more than 45 metres long and can carry a 37-tonne load, is described by the MoD as a versatile standby which can be used for surveillance.

It is being used to alert the coastguard and Border Force boats to migrant crossings, making use of its wide field of vision.

The cost of the operation is unknown but it is part of an “initial offer of assistance” from the MoD while discussions continue on any further military involvement.

After leaving RAF Brize Norton in Oxfordshire at around 7.10am on Monday, the aircraft flew over the Channel between Dover and Calais for several hours, according to the Flight Radar 24 website.

The rotor-powered grey cargo plane was seen circling low above the Channel during the morning, making several passes above the water, sharing the skies with a coastguard plane.

An RAF Atlas A400M above Dover
An RAF Atlas A400M above Dover (Gareth Fuller/PA)

Andy Netherwood, a defence commentator and former RAF pilot, said the A400M is “perfectly capable of finding boats and rafts”, has a good radar and has crews trained in maritime surface search as seen in the Falklands.

But, in a series of posts on Twitter, he added: “Whether this is a sensible use of an A400M is another question though.

“Preventing illegal immigration is a Home Office responsibility. The Home Office lacks capability, partly because it cancelled its aerial surveillance contract with Cobham in 2016.

“At the time James Brokenshire told Parliament ‘Border Force will ensure it retains appropriate air surveillance capabilities to meet continuing operational needs’. This clearly isn’t the case.”

A £4 million aerial surveillance contract designed to stop migrants crossing the Channel was scrapped by the Government in early 2016.

Then home secretary Theresa May cancelled the programme to save money despite warnings from Baroness Neville-Jones, a former security minister and chairwoman of the Joint Intelligence Committee, that it was a risk to Britain’s border security, according to media reports at the time.

Mr Netherwood said the work of the A400M could be carried out at a “fraction of the cost” by other aircraft.

He said the MoD is diverting the aircraft from defence tasks because “Priti Patel needs to appear tough on illegal immigration despite her department’s failings”.

“Illegal migration across the Channel is neither new nor unexpected,” he added.

“That said, the use of military aircraft to provide surveillance to direct Border Force vessels to suspicious vessels makes more sense than using Royal Navy warships.

“We can only hope that isn’t the next thing on the horizon.”

He called for a “comprehensive strategy” to address the root causes of the crossings and a “properly resourced” Border Force and National Crime Agency.

In December the Civil Aviation Authority said drones would be monitoring migrant boats attempting to reach the south coast between Eastbourne and Margate.