The PR industry's trade body has written to its members to find out if any of them were involved in producing a Government benefits leaflet which featured made-up characters and quotes.

The Chartered Institute of Public Relations (CIPR) has described the fabricated testimonies in the Department for Work and Pensions leaflet as "naive and opaque" and in breach of its ethical code.

It has written to PR companies to warn they will be held accountable if they were involved in producing the leaflets and have broken the code.

Work and Pensions Secretary Iain Duncan Smith faced sharp criticism after his department was forced by the Welfare Weekly publication to concede "Sarah" and "Zac" did not exist and the images on the leaflet were stock photographs.

The DWP insisted the case studies were "based on conversations our staff have had with claimants" and were dreamed up "to help people understand how the benefit system works".

Sarah Pinch, CIPR president, said PR companies must show a regard for the public interest.

She said: "Falsely creating the impression of independent, popular support is a naive and opaque technique which blatantly disregards the CIPR's standards of ethical conduct. It is deeply disappointing if public relations professionals allowed it to be published.

"All CIPR members are publicly accountable for the standard of their professional conduct, and the conduct of those under their management. This accountability is a valuable asset to the public, to members and to those who employ them.

"Honest regard for the public interest; delivering reliable and accurate information; and never misleading clients, employers or others are vital components of proper professional practice.

"Any CIPR member found to be breaking any of our ethical principles will be held accountable for their actions."

It is unclear whether any PR firms were involved in drawing up the leaflet. Fabricated quotes have also emerged in another DWP document.

In the original leaflet, "Sarah" was quoted as expressing delight at having been persuaded to draw up a CV under threat of having her payments docked.

"My benefit is back to normal now and I'm really pleased with how my CV looks. It's going to help me when I'm ready to go back to work," the quote said.

"Zac" was more conscientious, telling readers he had not missed out on any benefits because "I had a good reason for not going to the meeting and proof of the appointment".

Initially the DWP did not rule out continuing to "test" the original version with the fictional characters alongside one where the pictures were silhouetted and a note was added that they were "illustrative".

However a spokeswoman said that approach had been abandoned.