Assistant Defence Minister Stuart Robert has ordered the department to follow a lowest-cost travel rule.

Assistant Defence Minister Stuart Robert has ordered the department to follow a lowest-cost travel rule. Photo: Andrew Meares

A crackdown on Defence Department travel will save $76.4 million in 2013-14, with up to $300 million in savings expected over the next four years.

Assistant Defence Minister Stuart Robert has ordered the department to follow travel rules that require the lowest-cost airfare be purchased.

Mr Robert said Defence employees would not be stopped from travelling when necessary, and that "we are simply enforcing the policy". "We are saying we are not stopping travel - travel when you need to - but we have got video conferencing, let's use it, we have got phones, let's use them," he said.

In February, just 56 per cent of fares bought were the lowest available, with the other 44 per cent more expensive flexible fares.

That has since risen to 70 per cent of fares being the cheapest, helping produce $76 million in savings, which will be ploughed back into Defence capability.

Mr Robert said Labor had ordered a blanket 20 per cent travel cut, but "we are not going to do that. We are saying to do your job, we'll watch it because it is our job to be careful with public money. But ... the idea that 44 per cent [of flights] are flexible because you need flexibility, it's rubbish.

"We are down to about 30 per cent [of flights] needing to be flexible and we are getting down to about 20 per cent, which is about right. So we are getting some real efficiency into the organisation."

The savings mean the department will come in under budget for domestic and international travel in 2013-14, with $320 million spent on travel rather than the $396.4 million budgeted for.

About 100,000 people work for Defence, including serving soldiers, reserves and bureaucrats, and it is by far one of the biggest purchasers of air travel.

The department spent more than $1.3 billion on travel in the last three years of the Labor government: $455 million in 2010-11, $478.4 million in 2011-12 and $367.6 million in 2012-13.