Xenophon seeks apology from CFMEU

South Australian senator Nick Xenophon has demanded an apology and retraction from the Construction, Forestry, Mining and Energy Union, over material he says is defamatory.

The senator says he has sent the union a concerns notice under SA's Defamation Act over the "unprecedented" personal attacks on him.

He says the attacks relate to an amendment to the ABCC legislation before parliament that shortens the transition period for businesses to comply with a new building code.

On the CFMEU's website, the union says the senator has "betrayed people in his own state by doing a deal with Turnbull".

It says that move will make workplaces less safe, put more overseas visa workers on building sites, cut the number of appreciates in SA, threaten job security and fail to mandate Australian-made products on construction sites.

The sentiment has been echoed in billboards in Adelaide, in a full-page advertisement in The Advertiser newspaper, in TV ads and in robocalls.

Senator Xenophon said issues he had advocated for over the years showed the union's campaign was based on "hideous lies".

"It needs to be asked if this campaign is about damaging my vote and the vote of candidates I'll be supporting who will be running at next year's SA state election," he said in a statement.

The senator supports the government's original intention of a nine-month transition period for businesses to comply with a new building code, instead of a two-year period, but wants the changes to be the subject of a Senate inquiry.

Along with the concerns notice he has challenged CFMEU national secretary Michael O'Connor to a debate in Whyalla over the steel industry.