The Abbott government is reportedly preparing to sell off Medibank Private for $4 billion without having received expert advice on whether to do so and how.

A team of corporate spin doctors began drawing up plans weeks ago to sell the idea for a full or partial privatisation of the health insurer, Fairfax Media reports.

Newgate Communications, whose 10 senior executives include four former Liberal government staffers, is being paid $2000 a day to devise a communications strategy, it says.

Finance Minister Mathias Cormann has repeatedly said that no decision has been made on the timing or structure of a sale.

In November, Mr Cormann appointed investment bank Lazard to do the scoping study that was to be the trigger for a possible privatisation of Medibank.

It has until the end of February to advise on a method of sale, timing and estimated proceeds.

Labor says the government has already decided to sell Medibank without waiting for advice.