Medibank sale won’t hit premiums: Govt

The share sale process for the nation's largest private health insurer – covering almost four million Australians – has begun with a government campaign to get mum-and-dad investors to register their interest.

Finance Minister Mathias Cormann insisted that the insurer's ownership was irrelevant when it came to setting premium costs.

"Medibank Private will continue, in private ownership, to have to compete for customers and that will provide a limit to what can happen to premiums," he told ABC Radio.

But shadow assistant treasurer Andrew Leigh is unconvinced.

"Labor is certainly concerned about the impact it has on consumers," he told ABC Radio.

Senator Cormann declined to reveal the government's advertising spend on promoting the sell-off, saying it was consistent with previous privatisations.

The first stage of the Medibank sell-off is tipped to raise about $4 billion for the federal coffers.