Liberal Upper House candidate Wade De Campo has been caught lying on radio after ringing ABC Radio to question Labor leader Mark McGowan under a false name.

Mr De Campo, who is also Manjimup's shire president, identified himself as "John" from Collie on air and described himself as "just a person on the street", but he was quickly identified by ABC staff who recognised his voice.

Mr McGowan said it was a strange and dishonest act.

"This is a dirty trick. By definition it is dishonest what he's done and I think [people] would expect better from candidates, particularly mayors," Mr McGowan said.

He said it was highly inappropriate and Premier Colin Barnett needed to explain if it was a deliberate part of the Liberal campaign.

"I need to know and I think West Australians need to know was that authorised by Mr Barnett and the Liberal Party," he said.

"It's pretty poor form when you have dishonesty and desperation by candidates less than two weeks out from the election."

Mr De Campo admitted calling under a false name, but insisted it was appropriate to quiz Mr McGowan on renewable energy.

"Yes it's dishonest to ring through as John, I do acknowledge that; however … [Labor spokesman for state development] Bill Johnston says there will be a 50 per cent renewable energy target in Western Australia," he said.

He later issued a statement, saying he had made a serious error of judgement.

"My actions were not authorised by the Liberal Party and I apologise for any embarrassment and offence that was caused," he said.

Mr Barnett described the incident as "silly".

"It was the wrong thing to do," he said.

"But my understanding is Wade has apologised, so you know, it was silly, it was wrong, but that's it."

"As far as I'm concerned that's the end of the matter … sometimes silly things happen in campaigns."

Premier falls victim to protest stunt

The stunt came just two days after Mr Barnett was caught out by anti-Roe 8 protesters at the start of the Rottnest swim in Cottesloe at the weekend.

Mr Barnett posed for photographs flanked by swimmers with anti-Barnett slogans written on their arms.

The Premier said he was unaware of the slogans and claimed he was tricked into the stunt, blaming the media for giving it publicity.

"I don't think it's the sort of event that people should try to get political advantage out of," he said.

Mr Barnett was in the Pilbara yesterday announcing his Government's plans to nominate the rock art on the Burrup Peninsula for World Heritage listing.

Mr Barnett unwittingly posed for a photo with Roe 8 protestors. ( Supplied: Danielle Loizou Lake )

He told reporters he was frustrated when the media did not focus on significant issues.

"I guess I get a little bit frustrated when I don't see some of the big issues getting the attention I believe they should, for example, World Heritage listing of the Burrup Peninsula," he said.

"There's quite a bit of commentary about what I consider to be trivial matters."

The Premier said there was not enough commentary or scrutiny of his political opponents, and some of the key initiatives Labor is proposing to implement if it wins office.

"I think I've come under a lot of scrutiny over my political career. I accept that. I think you get good and bad publicity," he said.

"What frustrates me in this campaign is there's been virtually no scrutiny of what the Labor Party has put forward."

Mr Barnett cited the example of Labor's "Medihotels" plan, which purports to cut health cots by giving patients an alternative to full hospital stays.

He said it is unclear whether Medicare or private health insurers would support it, and how it would be funded and staffed.

"Those questions just simply aren't being asked," he said.