All hunting with hounds on National Trust land could be banned in an unprecedented vote this autumn.

Trail hunting – in which hounds and riders follow a scent that was laid earlier – is still allowed on trust estates but has long been regarded by animal rights campaigners as a means of circumventing the hunting ban. Now 50 trust members, including the explorer Sir Ranulph Fiennes, have endorsed a motion that will be debated at the trust’s AGM in October which would revoke all licences allocated to hunts.

“These hunts are still killing foxes, hares and stags – and they are being allowed to do so on National Trust land,” Fiennes said. “Hunting is despicable, cruel and has no justification in modern Britain. If the National Trust wants to truly preserve and protect our environment, it needs to stop condoning hunting, in any guise, immediately.”

A total of 79 annual licences were granted last year to applicants seeking to engage in trail hunting on trust lands, the organisation told the Observer. In accordance with the law, licences are granted on the understanding that the hunt simulates a traditional chase but without foxes being deliberately pursued or killed.

But according to the League Against Cruel Sports, which is working with the trust members behind the motion, hunts are being carried out as before the ban, with trail hunting providing “plausible deniability” to hunts when live animals end up being caught by hounds.

Philippa King, the league’s acting chief executive, said that the trust had been shown video footage of hunts chasing and killing stags on its lands and there appeared to be “no will” to stop it.

“We know the majority of people in this country want hunting to stay illegal, and we know they are shocked to find out it still goes on illegally,” she said. “The groundswell of public opinion against the National Trust allowing hunting is already massive and growing by the day, as more people realise it’s happening.”

The motion, put forward by Helen Beynon asks that her fellow members “agree that the National Trust must stop issuing licences for trail hunting, ‘exempt’ hunting, or allowing hunts to exercise their hounds on National Trust land, to prevent potential illegal activity in breach of the Hunting Act 2004 and to prevent damage to flora and fauna by the hunt, hounds and followers”. Challenged about trail hunting earlier this year during a talk at Nottingham Trent University, Dame Helen Ghosh, the departing head of the trust, said that the issue had generated a lot of correspondence on social media and that she knew of scores of members who had left because of the issue.

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“I would imagine that there are other members who would take the other view,” added Ghosh, who will leave the trust next March and become the first woman master of Balliol College, Oxford.

“Our position on trail hunting is that we believe parliament should be the judge of what is legal activity. We allow all sorts of activity on our land if it is legal.”

The trust had suspended licences in the past when holders did not adhere to terms, she added, and it worked with police on prosecutions. They include the Melbreak Foxhounds in Cumbria. The licence was suspended earlier this year for a day after a hunt monitor was attacked by a man who was later convicted of assault. In January, the trust said it would review its agreement with a hunt whose hounds reportedly attacked an elderly couple and their dog on a beach in Cornwall.

A trust spokesperson said: “We can confirm a members’ resolution has been submitted for our annual general meeting in October calling for the cessation of trail hunting on National Trust land. Members will have the opportunity to vote on the resolution and discuss the matter at the AGM.”

Polly Portwin, head of hunting at the Countryside Alliance, said that trail hunting had been adopted by the majority of registered hunts following the Hunting Act being enforced from February 2005.

“Many National Trust members regularly follow hounds and it is disappointing that they are effectively being accused of breaking the law while trail-hunting,” she said.

“To ban legal hunting activities on the grounds of protecting flora and fauna would suggest that dog walking and exercising horses across National Trust land should also be banned. There is nothing to suggest that hunts are regularly breaking the law while trail hunting either on private land or that owned by the National Trust.”

She said Ministry of Justice data showed that of the 423 people convicted of offences under the Hunting Act since it came into force 12 years ago, more than 94% did not involve hunts and were largely related to poaching and hare coursing offences.