Attorney-General George Brandis says the private member's bill introduced by Greens MP Adam Bandt – which aims to smooth the way for employers who want to pay their female staff more superannuation – is unnecessary, putting him at odds with the industry.

Mr Bandt introduced his bill last year as part of efforts to bridge the super gender gap. Women typically retire with much smaller savings than men because they're paid less on average and often take time away from the workforce to raise children. On average, Australian men have $82,000 in their super accounts to women's $44,000.

Mr Bandt acted after the Association of Superannuation Funds of Australia (ASFA) complained that employers who want to pay extra super to women have to apply for a legal exemption or risk falling foul of the Sex Discrimination Act (SDA).

But Senator Brandis has now written to Mr Bandt to tell him the government will not support his bill.

He says current laws don't actually prohibit employers from paying higher super contributions to women because they already allow for "special measures" to achieve gender equality.

"On this basis, the government considers that your bill is unnecessary to achieve the outcome you propose and accordingly we do not propose to support your bill," Senator Brandis says in the letter, obtained by Fairfax Media.

His views align with those of Sex Discrimination Commissioner Elizabeth Broderick, who believes the special measures provisions protection employers from legal action.

But ASFA head Pauline Vamos says she is surprised by Senator Brandis' comments. "That's not our advice. It's not what many lawyers say," Ms Vamos told Fairfax Media.

ASFA recommended the legal changes as part of a major report into the super industry last year. It argues the current system deters employers from paying women extra super, even if they want to.

The government's decision means the bill is doomed but Mr Bandt has vowed to press ahead, arguing businesses need more certainty than current laws offer.

"George Brandis' word isn't a 'get out of jail free' card," Mr Bandt said.

"Without a definitive law change, many companies may be reluctant to act because it relies on them being confident that the 'special measures' argument applies in their case."

Financial consultancy firm Rice Warner is believed to be the only company in Australia that pays its female staff more super – an extra 2 per cent – than it pays its male staff, in an effort to address the savings gap.

The company came up with the plan several years ago but found the law unclear, so they sought advice from Ms Broderick.

Ms Broderick told them they didn't need a formal exemption but Rice Warner's deputy chief executive, Melissa Fuller, believes the Greens bill would still help give businesses confidence and certainty.

"Businesses are risk-averse," she said. "We would support anything that's going to make it easier for employers to implement something like this if they want to – anything that removes red tape or uncertainty for employers."