Parliament's privileges committee investigated Mr Setka after he said crossbench senators Rex Patrick, Stirling Griff and Jacqui Lambie would "wear the consequences" if they voted for a union-busting bill.

But a report found the expletive-laden comments, which became public through a leaked recording of a shop stewards' meeting, didn't need further scrutiny.

"The committee reports that it does not consider the alleged conduct warrants further investigation as a possible contempt," Labor senator Deborah O'Neill told parliament on Thursday.

The committee found Senator Patrick's interpretation was partly based on behaviour by other union officials towards former senator Nick Xenophon.

"While the committee does not condone Mr Setka's comments, any substance to the alleged threat appears to be established by this link (to Mr Xenophon) and the media report," Senator O'Neill said.

In the leaked recording, Mr Setka said the senators would could expect to be abused on the street in 20 years' time.

"Someone is going to point the finger and say, 'There's them f***ers that voted for that bill that f***ed up not just construction workers but all workers in Australia'," he said.

The "ensuring integrity" bill that sparked the row is expected to come before the Senate during the final sitting fortnight, which begins on November 25.

Australian Associated Press