Still of video posted on Facebook site of Karen Baker showing officer emerging from the long grass after seemingly relieving himself

The officer was filmed by a woman in a nearby car, who saw him running into some tall grass as she waited for a loyalist parade to pass by.

The Police Federation – which represents officers’ interests and has roughly 6,500 members – has said the policeman was clearly trying to be “discreet”, and expressed hope that no action will be taken.

Karen Baker took the footage and subsequently shared it via the website Facebook.

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The Antrim-based mother-of-one was waiting on the edge of New Mossley estate in Newtownabbey between about 2.30pm and 3pm on Saturday, close to Glengormley Gospel Hall.

Her husband was taking part in a march with the New Mossley Sons of Ulster band, and as she heard the band approach, she saw the policeman by the main road hand his hat to another officer and run across the grass.

Mrs Baker wondered if he had perhaps seen something suspicious. “But whenever he started running towards the bushes you could quite clearly see he was pulling down his zip,” she said.

The footage shows that after the officer had finished, two young males emerged from a nearby pathway.

Mrs Baker said they were aged perhaps in their early teens, and that one of them remarked upon what the officer had been doing.

“I know people can be caught short,” she said. “But at the end of the day he’s an officer of the law – he’s supposed to be setting an example.”

She added: “I know he was facing away. But there was bound to be somewhere a bit more discreet he could have went to.”

She had not contacted the police to make a complaint about the incident.

The Police Federation said in a statement: “An officer’s behaviour is governed by PSNI Regulations. We are not aware of the full circumstances of the matter. Clearly, the officer has tried to be discreet and was mindful of the need not to cause offence.

“We note no complaint has been made and hope that this can be the end of the matter.”

However, the PSNI themselves issued a statement in the name of Chief Inspector John Allen from Antrim and Newtownabbey District.

It said: “We are aware of this footage.

“This is a matter of concern for us and as a result we have informed the Police Ombudsman.”

It added that anyone wishing to complain should contact the ombudsman.