Scott Morrison has warned a Labor government would tie businesses up in “union knots” after Bill Shorten refused to rule out supporting a return to sector-wide bargaining.

The prime minister is ramping up the rhetoric on industrial relations after unions dialled up pressure on the ALP to support plans to overhaul workplace laws.

The Australian Council of Trade Unions wants workers in the same job to be able to negotiate pay agreements across industries, arguing enterprise bargaining has failed.

Mr Shorten isn’t ruling out supporting the ACTU’s push for a return to industry-wide bargaining.

“The coalition has no plan to lift wages in this country, so I do think it is time to examine how we can improve the level playing field for millions of Australian working people,” Mr Shorten told reporters in Melbourne.

But Mr Morrison is adamant Labor will let the ACTU run the country if elected.

Small business will suffer if Mr Shorten makes changes to the way the industrial relations umpire makes decisions on wage disputes, the prime minister said.

“Bill Shorten will increase their taxes, increase their regulation and tie them up in union knots,” Mr Morrison told reporters on the Gold Coast.

Mr Shorten said under the coalition government, everything was going up except wages.

“We need to see wages moving again,” Mr Shorten said.

The ACTU’s Change The Rules campaign is in full swing, with a month-long advertising blitz kicking off on Sunday and rallies around the country planned over coming weeks.

ACTU secretary Sally McManus says unions want a fair go for working people by giving them stronger rights.

Industrial Relations Minister Kelly O’Dwyer said if Mr Shorten and Ms McManus were serious about boosting prosperity they would promote cooperation between business and employees.

“Sally McManus’ manifesto is a recipe for industrial conflict and chaos not seen since the 1970s, when industrial action was 40 times higher than today,” Ms O’Dwyer told AAP.

– AAP