Fairfax Media has reported the company is set to slash 900 jobs in a move designed to save $90million a year.

It is understood Australia Post has been reviewing its business model amid falling revenues in its traditional mail service.

Melbourne and Sydney are expected to bear the brunt of job losses, with smaller numbers of positions to be shed elsewhere around the country.

The Communications, Electrical and Plumbing Union said it was unclear to what extent the cuts would affect Tasmanian workers.

"There has been no specific figures or information provided to us as to how the state will be affected," CEPU state secretary Trevor Gauld said yesterday.

"Job losses have not been ruled out."

Mr Gauld said the union had been in ongoing discussions with Australia Post about how the business could deal with declining revenues.

"We are aware there is a need for ongoing structural change within Australia Post," he said.

"But underlying revenue issues should be dealt with in a sensible way, not by taking the shortcut of slashing and burning jobs."

Doubt has also been cast over the future of daily mail delivery, with Australia Post executives lobbying the government to allow the company to reduce its five-day mail service to three days a week.

An Australia Post spokeswoman said the company had made it clear it was confronting dramatic change due to declining revenues in its letters service.

"Without reform, the letters services will lose over $1 billion annually in a few years," the spokeswoman said.

But Mr Gould urged the federal government to reject any proposed changes to daily services, saying Australia Post had an obligation to deliver mail every weekday.

"Australia Post has a social contract with the people of Australia to deliver mail from Monday to Friday," he said.

The state government would be seeking a briefing on the mooted changes, a spokeswoman said.