Unions are pushing to improve the security of casual workers by having a clause introduced into modern awards allowing them to become permanent employees.

The Australian Council of Trade Unions is preparing to lodge a claim with the Fair Work Commission as part of its review of the modern award system.

The Fair Work Commission will be required to make a ruling on the ACTU submission and its final decision will become part of the award, which is reviewed every four years.

ACTU president Ged Kearney said it was unfair that casual employees who worked regular shifts and rosters missed out on sick leave and annual holidays. The ACTU submission would not apply to genuine casuals such as students working irregular shifts in bars or restaurants.