Whitehall is not getting value for money from its many offices, Parliament's audit watchdog has said.

The National Audit Office has estimated that £330m could be saved from the £6bn paid by departments each year for their premises.

In a report published on Wednesday, auditors identified wide variations in the amounts departments spent, and criticised Whitehall's failure to grasp sustainability issues.

NAO head Sir John Bourn said: "Government departments have a challenging time ahead in addressing the efficiency of their office accommodation.

"There are positive signs of departments beginning to engage with the issue, but there is still a vast amount of change required. Government is still a long way from achieving full value from its office estate."

The NAO has told departments that they need to "actively engage" with the Office of Government Commerce's 'high performing property' initiative, which aims to save £1.5bn annually by 2013.

While the departments have made a good start - nominating property champions, asset management boards and making benchmarking mandatory - the report said Whitehall needed a better grasp of the factors affecting efficiency.

These include employee and workstation numbers, occupation levels and accommodation costs.

One area where government departments were particularly lacking knowledge was on the environmental impact of their facilities.

Of the 877 buildings reviewed, there was no information on energy consumption for 265, on energy sources for 300 and on whether another 544 had recycling schemes.

When departments did have data, all relating to 2005.06, expenditure varied widely.

Median costs per square metre stretched from £123 at the then Department for Education and Skills to the £636 paid by the Department for Culture, Media and Sport. The report did add that the latter’s cost were expected to drop to £468 following a major rationalisation project.

Regional variations ranged from £507 per square metre in London to £133 in the North East. The NAO recommended that departments "fully explore" the option of moving to cheaper regions.

Square metres of office per person ran from 13.3 at the former Department of Constitutional Affairs to 21.9 at the Treasury. The OGC is currently consulting on a space 'standard' of 12 square metres per person, the report noted.

Costs per person were at their lowest at the DfES, at £2,592, compared to the £12,041 spent by the Treasury. The NAO said this was affected by the nature and type of building and noted that, since those figures were compiled, the Treasury had moved OGC staff into its main building and freed up two other buildings.

Liberal Democrat Cabinet Office spokesman Norman Baker said that, after years of the government lecturing on efficiency, it was "high time it put its own houses" in order.

"The prime minister always claims he is interested in 'prudence' so let him act now. What is needed is a determined programme that will both cut costs and the environmental impact of the activities of central government," Baker said.