Industry super funds and small businesses are at odds over the best way to stop employers from underpaying superannuation amid calls for tougher reforms to prevent businesses from dodging their obligations.

A senate committee held its final public hearing on Monday to consult on a tax integrity bill that would stop employers from being able to count an employee's voluntary salary sacrificed super contributions towards the required 9.5 per cent super guarantee payment.

Industry Super Australia's Bernie Dean. Credit:Peter Braig

A loophole in tax law has meant when workers salary sacrifice into their super funds, it has been possible for their employers to count this towards the mandated super guarantee amount and therefore pay staff less super.

There is widespread agreement that a change in the law is overdue, with Industry Super Australia claiming the law cost Australians $1.5 billion in lost super payments in 2016-17.