The monarchy won praise yesterday for a new-found skill to be envied by all travellers: negotiating discounts for airline tickets.

The national audit office reported that Buckingham Palace's travel budgeting had cut travel costs by more than two-thirds: rail and air travel costing £5.4m compared to was £17.3m. in 1998.

Since the royal yacht Britannia was decommissioned in 1997, the royal family has not travelled by sea. They meet the cost of their car journeys privately, so the budget relates to air and rail travel.

The NAO suggests that, while members of the family will continue to feel honour-bound to fly the flag on the national airline, members of their staff should be encouraged to seek lower fares elsewhere.

A spokesman for the NAO said yesterday: "We would expect members of the royal family to fly BA but there is no reason that members of the household should not shop around."

The report also reveals that, apparently alone among the travelling public, the royals have benefited from lower expenditure on rail fares even though the number of rail miles they have travelled has doubled. Spending on rail travel has fallen from £1.9m to £800,000 after negotiations with Railtrack, which owns the royal train.

The feat has been achieved by cutting the length of the train from 14 carriages to nine - the rest were sold off for £235,000, which went to the Treasury - though attempts to hire out the train when not in use have so far failed.

Even the Queen these days sometimes travels on scheduled trains, though when she does so an entire carriage is hired.