Casuals generally earn $11.59 less per hour than permanent workers, or an hourly rate of $28.95 against $40.54, a pay gap of 28 per cent, Australian Council of Trade Unions research shows.

The pay differential is the highest on record.

Employees with the same skill level or occupation had a smaller pay gap of between $3.55 and $3.84 an hour, equating to a discrepancy of about 11 per cent.

The union noted the gap existed despite casuals receiving a pay loading of up to 25 per cent and it called for the Albanese government to scrap “Morrison-era changes to the law”.

The government should also introduce a common-sense definition of casual work as part of its industrial relations reforms because too many jobs were casual “in name only”, it said.

“Too many jobs that are actually permanent jobs have been made casual, denying workers both pay and rights,” ACTU secretary Sally McManus said.

“The majority of casuals work regular hours, week in, week out and have been in their job for more than a year.

“Changes made by the Morrison coalition government in early 2021 made this erosion of job security completely lawful.”

The increased pay gap was hurting casual workers, with 50 per cent reporting they were financially worse off than they were 12 months ago, the union said.

Almost one in four Australian workers are casual and women comprise 55 per cent of the casual workforce.

“Big business has used loopholes in our work laws to make what should be secure jobs into casualised, insecure work. It is a way of driving down wages and putting all the stress onto workers,” McManus said.

“We need to close these loopholes so workers who are misclassified as casuals and underpaid can gain job security and have jobs they can rely on.”

The Fair Work Commission should be empowered to quickly determine who was and was not casual, McManus said.