Contractors will be invited by the Treasury to join the debate into the future of public spending as part of chancellor George Osborne’s “fundamental re-evaluation of the role of government”.

The Treasury will canvas opinions on which functions the government should perform and which could be done by other bodies to save money.

A “star chamber” of senior figures will also be created which ministers will have to justify their spending in front of.

The move comes as David Cameron warned that spending cuts would need to be severe because interest payments on the national debt could hit £70bn within the next five years.

Osborne is expected to outline the consultation framework for future spending decisions at Treasury questions in the House of Commons later today.

The model copies a scheme from Canada’s successful deficit-cutting strategy from the 1990s.

It will ask people to discuss whether the government needs to provide certain public services at all, or whether other organisations, such as councils, voluntary groups or companies, could do so more cheaply.

A Treasury official said: “Anyone who thinks the spending review is just about saving money is missing the point.

“This is a once-in-a-generation opportunity to transform the way that government works.”

One contractor told the Enquirer: “It seems Cameron is preparing everyone for deep cuts.

“Talking to industry is a positive thing and there should be areas where private money can come in and pick-up the slack.”