Last week, Agriculture Minister Terry Redman issued a media statement saying the Labor Party had proved itself to be dishonest or incompetent in its "latest commentary" on GM crops.

The attack came after Mr Murray's statement earlier in the week that claimed the shires of Manjimup, Plantagenet, Boyup Brook, Bridgetown-Greenbushes and Denmark had all made formal declarations against the growing of GM crops.

Mr Redman said this statement was blatantly untrue.

"Either Mr Murray has failed to do his research or he is happy to deliberately mislead the WA public," he said.

The Shire of Plantagenet changed its stance on GM's at a meeting on April 29.

It supported a motion declaring its concerns about GM canola trials had been satisfactorily addressed.

WA will host 20 large-scale trials of GM canola; 17 on farms and three at Agriculture Department research sites.

A spokesperson for Mr Murray said the information they had at the time was based on advice given on April 3 from the Western Australian Local Government Association (WALGA) and the shires' websites, and proved to be "slightly inaccurate" regarding Plantagenet's position on the GM trials.

He said Greens MLC Paul Llewellyn had incorrectly said on his website that the Manjimup motion was carried in February 2009.

"Mr Murray must be getting his information from this source because he's too lazy to do his own research," Mr Redman said.

Mr Murray said he had not personally responded to Mr Redman's claims of mistruths and was surprised to hear about the Shire of Plantagenet's position.

"Can you tell them to update their website," he said.

"We went off the best of what we knew at the time."

Mr Murray said the information about Plantagenet came from information in a letter his office received from WALGA.