A QSuper member has been told his fund will be reduced by almost $290,000, after undetected administrative errors left hundreds of accounts incorrect for years.

About 100 members of one of Australia's largest superannuation funds have been asked to pay back tens of thousands of dollars as a result of the errors, which were only discovered after a recent investigation, but date back more than a decade.

At least one member will be $290,000 worse off, and is among many others who have been overpaid, while another 246 members have been underpaid.

A QSuper spokesman said the mistakes were traced back to a "legacy administrative error".

"We have identified how these errors occurred, introduced additional training and systems controls and engaged an independent auditor to ensure we have appropriately addressed the underlying isolated issues," he said.

'Q in Qsuper stands for questionable'

QSuper began contacting the affected members in the last fortnight, with one senior public servant — who is preparing to retire — telling ABC News he was shocked after being told he would be $90,000 worse off.

"They are not working with me to help me address the shortfall in my account due to their poor administration, as they claim," he said.

"There are no options for me to make up the significant shortfall — at a point where I am bordering on retirement.

QSuper says the mistakes were traced back to a "legacy administrative error". ( qsuper.qld.gov.au )

"There is no offer of compensation for their long-term negligence.

"The bottom line on all this is, they have made me … accountable for their staggering mismanagement of my nest-egg and that for me is the mark of a very poor organisation.

"I now understand the Q in QSuper stands for 'questionable'."

Another member has been asked to repay more than $20,000 within 60 days, despite retiring five years ago and said if he had known earlier, he may not have sold his house.

"Both my wife and I were shocked and distressed to receive this news out of the blue," he said.

"This has caused sleepless nights and increased worry for us both to be confronted with a claim so long after I had retired.

"Had we known this error was to be visited on us, we would not have made that decision and, in fact, I may have continued to work until we thought our financial position was sufficient for our future needs."

The member received a letter last month notifying him of the problem, indicating the error stemmed back to 2007.

Mistakes linked to family break-ups

The multi-award-winning superfund said most of the miscalculations came about from errors made after family break-ups, where superannuation assets between ex-partners were split.

However, the two members who have spoken to ABC News said this was not the case for them.

QSuper staff have since "unreservedly" apologised for the errors.

"It is now apparent that the instructions to reduce these members' accounts, which QSuper is obligated under law to undertake, were not processed correctly," said the QSuper spokesman.

"One of our core principles is ensuring our members are always treated fairly and equitably."

Half of QSuper's board is appointed by the State Government, with four large unions in charge of appointing the other half.

'Unacceptable situation': Treasurer

Treasurer Jackie Trad said she was unaware of the situation before being contacted by ABC News.

"This is clearly an unacceptable situation and I am very concerned by these reports," she said.

Jackie Trad will be seeking a briefing from QSuper on the measures they've put in place. ( ABC News: Patrick Williams )

"I have been assured by QSuper that they are working proactively with those impacted to mitigate potential disadvantage.

"I understand that a large number of these miscalculations are to do with complex family law matters around the division of assets.

"I will be seeking a briefing from QSuper on the measures that they have put in place to ensure that this does not happen again."

Opposition Leader Deb Frecklington urged the State Government to intervene.

"Labor need to come out today to explain how they are going to fix this mess — taxpayers shouldn't be out of pocket because of Labor's bungle," she said.

Some members who spoke to ABC News said they were seeking legal advice about their options, with one engaging a lawyer to help deal with the superfund.