Unions have declared war on Scott Morrison's government, as they rally the troops for an electoral showdown on penalty rates, insecure work and stagnant wages.

ACTU secretary Sally McManus said Mr Morrison's election had sparked an influx of volunteers ahead of this weekend's National Door Knock, with activists preparing to push the message in key electorates that the new Prime Minister and his cabinet are "out of touch".

It comes as newly sworn-in Industrial Relations Minister Kelly O'Dwyer prepares to meet with business leaders - and at least one of her predecessors - as she comes to grips with one of the most fraught portfolios in the new cabinet.

Australian Council of Trade Unions secretary Sally McManus has declared war on Scott Morrison's government. Credit:AAP

Ms McManus, who has been criss-crossing the country in recent weeks to launch the ACTU's Change the Rules campaign at trade halls and workers' clubs, said the number of people showing up to events was growing steadily.