Former police officers are to be issued with identity cards they can carry around in their wallet to acknowledge their service.

New South Wales Police plans to hand out the first ID cards by the end of the year.

Chair of NSW Police Legacy Acting Inspector Paul Bousfield said traditionally when officers left the force they were asked to return their identification (their warrant card).

"The retired police officer's identification card is a wonderful initiative because it returns the identify of a former police officer back to them," Acting Inspector Bousfield said.

Ex-police officers will be able to lodge their applications for a card at a police expo to be held in Sydney in October.

Cards absolutely absurd: Council for Civil Liberties

Stephen Blanks from the NSW Council for Civil Liberties described the plan as "extraordinary".

"The idea of issuing a card to former police officers is absolutely absurd.

"It is entirely predictable that it will be used by former police officers to get favours from shops and local businesses, who will feel intimidated into giving free goods and services because of a concern that putting a former police officer offside might cause them trouble."

He said such a card could also be used to fool people into thinking the holder still held a position of authority.

"What other professions might ask for cards? Former university professor? Former politician?"

But Acting Inspector Bousfield said he had no concerns the cards could be misused and would not provide any perks to the owner.

"There's no benefit that could be derived from the card in terms of financial opportunities or preferential treatment," he said.

"It really is something that's precious to the owner."