Unions have suggested non-members should pay a fee to cover the costs of negotiating higher wages and better conditions.
With declining memberships across several industries, the Australian Manufacturing Workers Union wants laws rewritten to encourage take-up and give delegates and organisers greater powers.
The union says its members have to do more of the fighting for decent pay and conditions that benefit non-union workers.
One proposal would have non-union workers required to contribute a fee to a union.
"Imagine walking into a fishing club or a footy club and demanding all the benefits without being a member. You wouldn't even get through the door," AMWU national secretary Steve Murphy said.
"Many thousands of workers benefit from the outcomes of collective bargaining agreements fought for by unions, but don't join union members in the fight for higher wages, safer conditions and better workplace rights."
The Health Services Union said non-members should stop getting a free ride.
It has spent $1.2 million pushing for a 25 per cent pay increase for aged care workers.
"A lot of effort goes into that," HSU national president Gerard Hayes told AAP.
"The pay rise helps change their lives, it helps change their communities."
He suggested the equivalent of a one-year membership - $500 in the HSU's case - be levied on non-union workers to recognise the union's advocacy.
"If people choose to be a member of the union, great, if not that's a matter for them," Mr Hayes said.
"The last two-and-a-half years of COVID has shown we're a society that relies on each other and we need to support each other."
Opposition workplace relations spokeswoman Michaelia Cash said it was disgraceful to take people's money for services they didn't ask for.
"It is nothing more than the ailing union movement's way of propping up their declining membership," she told AAP.
Senator Cash said the Albanese government's industrial relations reforms, which it kicked off last year by expanding multi-employer bargaining rights, opened the door to "more outrageous demands from the unions".
"Australians have the right not to join a union and they should never be forced to do so," she said.
Australian Associated Press