Casual workers should have the option of becoming permanent and those in the gig economy should have equal work rights, the nation’s union movement says.

The Australian Council of Trade Unions stepped up its campaign for an overhaul of workplace laws on Wednesday as the Turnbull government accused the movement of pushing “left-wing lunatic” policies.

ACTU secretary Sally McManus told the National Press Club on Wednesday the current system meant employers could keep workers on as casuals while they were effectively permanent staff.

Last year the Fair Work Commission rejected an ACTU push that meant employers would not be able to deny any reasonable request from a worker to become a permanent employee after six months.

On Wednesday, Ms McManus said casual work needed to be “properly defined and workers given the right to opt for a secure job”.

“Our current laws do not properly define casual work. As a result, workers can remain casual for years – the average tenure of a casual is around three years – not because all those people want casual work, but because they are given no other option,” she said.

Workers deserve the right to convert to permanent work if they want and to negotiate for job security protections.”

Casuals are currently paid a 25 per cent loading because they do not receive benefits such as sick leave or annual leave.

Under the current system, workers can request flexible working arrangements and take parental leave after one year.

But Ms McManus argues employers are under no obligation to accept those requests.

Small Business and Workplace Minister slammed the ACTU’s proposal, saying the current system worked best.

“You have the right to ask, but the employer has the right to decline,” he said.

“That’s the Fair Work Commission’s decision. Not mine.”

Earlier this month, the ACTU launched the ‘Change The Rules’ campaign, its largest since its efforts to defeat John Howard’s WorkChoices.

The campaign aims to convince the major parties to commit to reform workplace laws, with the union movement warning that the system was broken.

“Casual work has increased, sham contracting continues unchecked, labour hire is growing, contracting out continues and the so-called gig economy is expanding,” Ms McManus said.

Labor has indicated possible support for some of the proposals, but the Coalition has slammed them.

Asked why she thought Labor had not been more supportive, Ms McManus said on Wednesday: “In terms of political parties, maybe it takes them a while to catch up.”

Mr Laundy said it was a “lie” that casualisation was increasing.

It had stayed constant at 25 per cent for the past two decades he said.

“Casual work is a completely appropriate way for many businesses and employers to conduct their relationship,” he told ABC Radio National.