Under a workplace deal between Jeld-Wen Glass and its employees, an entitlement to a combined 10 days' annual sick and family leave is paid as a weekly allowance of about $32.
In exchange for the weekly payment, ill employees are not paid when they are off work.
The Construction Forestry Mining and Energy Union has launched Federal Court action seeking penalties of almost $700,000 against the company for alleged breaches of federal workplace laws.
Leo Skourdoumbis, assistant national secretary of the union's forestry and furnishing products division, highlighted the company's sponsorship of St Kilda to attack the agreement.
"This is a company that sponsors the St Kilda Football Club where their best player, Nick Riewoldt, just had a prolonged period of time off because of an injury and he got paid," he said.
"But if our members, who are employed at the same company, have to have time off because they were sick or are injured at work, they would not get paid."
The clause was originally contained in an Australian Workplace Agreement that was struck in 2006 under John Howard's Work Choices regime.
The CFMEU said the clause continued to be imposed on the employees despite the laws being changed under Julia Gillard.
In court documents, the union said the workers were now covered by an individual transitional agreement that stipulated that sick and carer's leave could not be cashed out if it resulted in their accrued entitlement being less than 15 days.
The union said each cashing-out of leave had to be done through a separate written agreement between the company and the worker.
Mr Skourdoumbis claimed the agreement clauses were a "relic of the Howard era" and should not apply to employees.
"We think it's immoral and illegal and we are going to prove that in the Federal Court," he said.
"It forces workers to come into work when they are sick just so they can get paid.
"You might have a prolonged illness . . . You might get injured at work as this is a glass factory. WorkCover doesn't kick in initially. You are then going to have to use some sick leave but you are not going to get paid."
A spokesman for Jed-Wen yesterday declined to comment.
The union is taking the action on behalf of a worker at the company's Rowville factory in Melbourne. It said about 25 to 30 employees were in a similar position.
Meanwhile, retailers will seek to overturn a Fair Work Australia ruling to maintain three-hour minimum working shifts for teenagers.
The National Retailers Association said yesterday it would appeal against the tribunal ruling, which it believes will result in job losses.
