A "fake review" of advocacy group Consumer NZ has prompted a reminder that online comments are not always what they seem.

Consumer NZ chief executive Sue Chetwin said a negative comment was posted about Consumer NZ's operations, and Flick Electric, on its website.

"We love comments and reviews. They help us improve what we do. They often provide good story ideas. This comment did neither. But it did raise suspicion.

123rf One marketing expert says it's a reminder that reviews of businesses may be posted by people with a hidden agenda.

"The reviewer rang our office shortly after it was posted, asking for it to be taken down. Not because of any remorse I suspect, but because her name was attached to it. It didn't take long to find out she worked for a [public relations] PR company, which counted a competing electricity retailer among its clients."

Chetwin said she was concerned that the PR firm's worker had questioned Consumer NZ's integrity.

"I'm not so naïve to think competitors wouldn't make comments on our site, just like they do on every review site," she said.

"[But] one of the beauties of belonging to us is that people trust our advice. We've built a business on it. I rang the PR woman who posted it. I wanted to know whether this was company practice.

"After some bluster, she apologised. She broke down. She said she realised, after it had been posted, it was foolish. Her managing director then phoned. She apologised too. The posting breached their own guidelines, she said."

Chetwin said she had decided not to name the companies involved.

Averill Gordon, curriculum leader for public relations at the Auckland University of Technology, said such actions breached the industry's code of ethics.

She said the second of the requirements in the Public Relations Institute of New Zealand code was that people disclose their conflicts of interest. "You can't talk about a client business without revealing you are their PR person."

She said while some laypeople might post reviews online with a vendetta, PR practitioners should know not to. "You're a professional consultant. The client is paying you to give them objective advice."

Mike Lee, a marketing expert from the University of Auckland business school, said people should take anything they read about brands with a grain of salt.

"Unless the review has been compiled by a reputable and independent source, such as Consumer NZ, or an independent research institute that has disclosed no conflicts of interest," he said.

"If a source has nothing to hide they should not be afraid to reveal their true identity, they should also be okay revealing their research methodology. Consumers should know that many online reviewers and bloggers do get paid or incentivised to review products. This is usually disclosed.

"It is less common for bloggers or employees to be paid to say negative things about competitors' brands, as this could get companies into legal trouble, in terms of defamation."