Australia’s most powerful union group wants to guarantee conditions for casual workers.

Casual workers do not have guaranteed hours, can be sacked without notice and are not eligible for sick leave or annual leave.

Casual staff are paid more, but Australian Council of Trade Unions (ACTU) secretary Sally McManus says employers are taking advantage of workers by keeping them on casual rates despite effectively employing them in a permanent capacity.

“The goodwill you get from giving loyalty to your employees and giving them that security they need to build a life is repaid back to you,” she said.

“Where people are disposable and they get treated like that, that's how they can sometimes feel towards their employers as well.”

Employees can ask for consideration of more benefits after a year of work, but the ACTU wants them to be able to convert to permanency after six months.

Small Business and Workplace Minister Craig Laundy says the measures are unnecessary.

“It is working exactly as it was designed to function,” Mr Laundy said.

“This is a left-wing lunatic attempt to reset [the ACTU's] business model.”

Ms McManus says employers are not obligated to accept requests for better conditions.

“The problem at the moment is, workers can request it but employers can just say no and there's no appeal to that,” she said.

“If workers are working regularly, if they are proper permanent workers, [they should be] able to get the benefits of being a permanent worker.”

Mr Laundy the current system of giving the boss the right to decide is working.