Devon and Cornwall police have apologised after an officer appeared to refer to animal rights activists as “idiots” at a badger cull briefing.

Undercover filming obtained by campaign group Stop the Cull reveals a police liaison officer advising farmers and marksmen involved in executing the policy on how to deal with activists and saying he would confiscate cameras set up to monitor badger traps.

The officer called the activists “idiots” on three occasions but warned against violence towards them, according to the video. However, he said in reference to previous situations: “I tell you what, some situations they were in, I’d have had trouble keeping my hands to myself.”

The south-west England force recognised the officer had not behaved in an “impartial manner” and said action would be taken against him.

“We expect our officers and staff to behave in a polite, courteous and impartial manner at all times and these high standards have not been met on this occasion,” a spokesperson said.

“We do not condone the language used by the liaison officer and we’d like to apologise for the views expressed. Once the full circumstances are established, the officer will be subject to appropriate management action.

“The officer will be closely supervised and any further suggestion of non-impartiality will result in them playing no further part in this year’s operation.”

The video, which captured 14 hours of footage from inside a farmyard building, also appeared to show ammunition being taken from a box on a table.

The spokesperson added: “We have been made aware of allegations and footage relating to the security of ammunition at a badger cull briefing in north Devon. Police inquiries remain ongoing at this time and any identified criminal offences will be dealt with robustly.”

Jay Tiernan, a spokesperson for Stop the Cull, welcomed the apology and called for all future meetings to be recorded and published “so the general public can see exactly how evenhanded badger cull policing is”.

“The police have once again shown they are in no way impartial when it comes to dealing with protesters,” he said.

“A police officer calling all protesters ‘idiots’ is at the very least insensitive and it was compounded by his further comment that he might have ‘trouble keeping my hands to myself’. We are wholly engaged in non-violent direct action and there are no situations where a police officer should be considering violence towards us.

“His comments that any of our trail cams found pointing at traps won’t be returned to us are staggering, considering that video evidence is vital to prove criminal activity.”

Activists have been taking direct action in the countryside to prevent the killing of badgers, which they say is cruel and unnecessary. The government adviser who led the scientific review on which the policy was based, Prof Lord John Krebs, has said the cull is not an effective way of controlling bovine TB.

However, the government has said the culls have resulted in disease reduction benefits for cattle.