AWU boss steps down after three years

The boss of one of Australia's biggest unions has announced his resignation.

Scott McDine said on Monday he was stepping down as national secretary of the Australian Workers Union after three years at the helm to take a "decent break" and consider what challenges to take on next.

Mr McDine spearheaded the campaign for a domestic gas reserve, led talks on the future of the steel industry and guided the AWU through the unions royal commission.

He said it was appropriate to sign his resignation before union election nominations opened shortly.

"Despite facing a federal government determined to undermine our strength and authority, I am proud of seeing our union through a long and difficult royal commission," he said in a statement.

Mr McDine was involved in the AWU for almost 20 years before seeking a full-time elected position.

He said he was confident assistant secretary Daniel Walton would receive the full support of members to lead the union.