Union weighs into Canning by-election

The building union has weighed into the Canning by-election, saying it's an opportunity to highlight problems with the China free trade agreement.

The CFMEU says the Abbott government is trading away local jobs, insisting the local market won't be tested before foreign labour is employed.

The claim has been denied by federal Trade and Investment Minister Andrew Robb, who dismissed the union campaign as "racist misinformation".

Mr Robb said the campaign was perverse because it was against new, job-creating investment.

"This operates under the existing guidelines - nothing has changed and the unions know it," he said.

"This is a racist campaign because identical provisions that are in this agreement were features of our FTAs with Korea, Japan and Chile, which Labor concluded, yet no concerns were raised about these."

CFMEU national secretary Michael O'Connor said the union wasn't racist and cared about foreign workers, who could be paid comparatively low wages under the deal.

"This by-election is a chance for the voters of Canning and also the whole community to express a view about the Chinese free trade agreement," Mr O'Connor told AAP.

"It's an agreement that undermines our job market. It's going to put downward pressure on wages and conditions. It will see visa workers exploited.

"Trade agreements should be about creating jobs," he said.

"We can get investment without selling off our sovereignty and selling away our jobs to other countries."

He backed Labor candidate Matt Keogh, saying the dispute resolution lawyer had lived in the Canning area, which suffered from rising rates of unemployment - especially among young people - and he understood the importance of job creation.

"I think he'll understand that we certainly don't need a bad free trade agreement if we're trying to do something about employment."