The short-changing affects more than nine in 10 workers younger than 18 and hits women harder than men, according to superannuation peak body the Super Members Council.
Employees aged 17 and under are only guaranteed superannuation payments if they work more than 30 hours a week for a single employer.
"More than half a million young Australians are missing out on a workplace right to super that 17 million Australians have – and that's just not fair,'' Super Members Council chief executive Misha Schubert said in a statement on Tuesday.
The law was denying young workers guaranteed contributions at a key point in their careers, the council said.
"The earliest contributions into your super make the biggest difference to how much super you'll end up with because they have the longest time to grow," Ms Schubert said.
A 16-year-old worker might miss out on up to $2500 in super contributions by the time they reached adulthood.
The issue also disproportionately affected young women because they worked more part-time jobs, leaving them $11,200 worse off by retirement, compared to $10,600 for men.
"For many women, (the gender pay gap) starts from their very first job," Ms Schubert said.
The Council of Small Business Organisations Australia said expanding super to teenagers must not come at the cost of overburdening small businesses.
"Small businesses are already managing rising employment costs, increasing compliance obligations and tight operating margins," the council's chief executive Skye Cappucio told AAP.
"Governments should be careful not to introduce changes that make it more expensive to employ young people."
Young people were more motivated by spending money than retirement savings, Ms Cappucio argued.
Expanding super to teenage workers was rejected in the Senate on July 1 when Labor and the coalition voted against a motion floated by Greens Senator Barbara Pocock.
At the time, Liberal senators raised concerns over small businesses already grappling with having to pay super in each pay run rather than every quarter.
That change – payday super – also took effect in July.
The jobs market for teenagers could shrivel up if young workers were more expensive to hire or if additional costs squeezed small businesses, the coalition argued during the Senate debate.
The Super Members Council has suggested a transition period for businesses to adjust to the proposed change, and calculated the impact as a share of total employee compensation after tax deductions would be 0.03 per cent.
Roughly five in six Australians agreed anyone who did paid work should be eligible for super payments, the council said.
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