Medibank has suffered an ‘unacceptable’ technology failure.

Australia’s largest health insurer has announced it will be unable to provide annual tax statements to the “majority” of its 3.8 million members by July 15.

In a statement on Thursday, Medibank chief executive Craig Drummond said the delay was the result of customer data migration and acknowledged it was “unacceptable”.

“I sincerely apologise to our customers for this disruption,” Mr Drummond said.

“It is important for customers to know their personal data has not been compromised. Our team is working around the clock to resolve this issue, and I want to assure customers that our focus is on minimising the impact this will have on them.”

Medibank CEO Craig Drummond. Picture: Aaron Francis/The AustralianSource:News Corp Australia

A Medibank spokeswoman told news.com.au while “we still have quite a few days to actually work through a solution, at this stage the majority of customers are affected”.

“Medibank is in the middle of upgrading its technology platform. As part of the data migration we’ve experienced an issue with reporting,” she said.

“We’re still working to resolve this issue. Overnight we thought we had in place a solution but that has not been successful, so we wanted to be open with our customer base.”

Medibank informed regulators this morning of the issue. AHM customers will not be affected.

The spokeswoman said the fault was internal and not the result of third-party contractors, but couldn’t say what the repercussions would be.

“At the moment our focus is on resolving this. We are working around the clock,” she said.

frank.chung@news.com.au