Prime Minister Scott Morrison says a vote for Labor in the May 18 federal election would give the unions and Greens too much influence and affect jobs growth.
Scott Morrison has launched a blistering attack on unions, warning ACTU secretary Sally McManus will effectively be on the board of all companies under a Labor government.
Speaking at a NSW Business Chamber function in Parramatta on Wednesday, the prime minister sharpened his criticism of the opposition over industrial relations.
"If Bill Shorten is elected, Sally McManus will now be a board member figuratively on every single one of your companies," he told bosses.
"The union movement will basically be in control of your businesses if the Labor Party is elected on the 18th of May."
Labor has promised to abolish the Australian Building and Construction Commission if elected.
Mr Morrison believes without the watchdog, the militant construction union would have free rein over the industry.
"They want control of the Australian building industry again," he said.
"They want control of every site. They want control of every decision you make."
He said a Shorten government would hurt the business sector with more environmental regulation.
"There'll be an army of green bureaucrats running around telling what you can and can't do in your business," Mr Morrison said.
The prime minister expanded on his criticism of Ms McManus, saying she had no problem with breaking unjust laws in 2017.
"Is there any wonder we're seeing people behave the way they are when you've got people in positions of authority saying the law doesn't matter," he said.
"If Bill Shorten is the prime minister, you can be sure that Sally McManus will get her way.
"She is the one, along with the union movement, who will sit effectively on every board in this country."
An ACTU spokesman said Mr Morrison was running a desperate scare campaign.
"Sally is not going to be on every board in the country. That's impossible and ridiculous," he told AAP.
"These comments from Scott Morrison show us what kind of leader he is - someone who will lie and attack his fellow Australians who just want a fair go for working people."
He said unions were pushing for fair pay, more secure jobs and decent rights at work.
Labor has promised to restore Sunday penalty rates, lift the minimum wage and protect the rights of workers and unions when they are negotiating enterprise bargaining agreements.
Later pressed on the coalition's workplace reform plans, Mr Morrison told reporters his government if re-elected would "protect changes" already instituted, such as the building industry watchdog.
"We have made some big changes and we're going to stand by and protect those changes," he said.