The prudential regulator will not set guidelines for the minimum size of a superannuation fund.

Australian Prudential Regulation Authority (APRA) supervisory support division general manager Greg Brunner said the requirement under Stronger Super for trustees to review on an annual basis whether the fund had sufficient scale would not include any absolute numbers.

"Considerations of scale is an area which has given rise to some uncertainty in the industry, but which in APRA's views should not cause great difficulty to implement," Brunner said at the Conference of Major Superannuation Funds 2012 in Brisbane earlier this week.

"The obligation of trustees is not to achieve a stated level of scale, but rather simply to determine annually whether their MySuper members are disadvantaged relative to their peers in other funds, because of the scale of the product."

He said disadvantages arising from lack of scale could be manifested through the inability of the trustees to negotiate competitive administration or investment management fees, or to access certain types of investment opportunities.

"There is some evidence that there is a correlation between scale and return, but APRA is fully aware that this is not always the case and effective trustees can operate a fund at a range of scale levels," he said.

"The legislation is not prescriptive of what should happen if the trustee forms a view that a lack of scale is disadvantaging MySuper members.

"The fundamental obligation is on the trustee to act in the best financial interest of the members, however, the way in which it does is left to the discretion of the trustee."

The majority of the upcoming 12 prudential standards placed responsibility in the hands of super fund boards, and APRA expected directors to develop policies in response to the standards, he said.

"The board needs to think about this; the board needs to have a policy. In our thinking, the board is ultimately responsible for RSE [registrable superannuation entity] activities."

APRA deputy chair Ross Jones said he hoped to release the new prudential standards next month.

Jones said they would not seek to dramatically change the industry, but largely consolidate existing practice.

"The superannuation industry will now be regulated in the same way as any other industry, that is to say any other industry that is regulated by APRA," he said.

"You will see that there is not a significant change in the prudential standards compared to what people are doing anyway.

"There will be some superannuation-specific standards on governance, conflicts of interest and there will be a specific standard on defined benefit matters.

"There will also be an operational risk requirement. Also, there will be a special transition-to-MySuper standard."

He said the timeline for the implementation of MySuper was tight and trustees should be in the development stage now.

"You have to think about MySuper now; you need to be talking to APRA now. Funds say: 'But I haven't seen the standards yet.' Well, we are sympathetic, but there is not a lot we can do about it," he said.