The government has defended the payment of bonuses to Ministry of Defence (MoD) civil servants following criticism of the practice.

It emerged that the MoD’s civilian 85,000 staff would share a bonus pot of £47m, but the home secretary said this morning that many officials did “difficult and sometimes dangerous” jobs, including visiting frontline troops.

"I think we need to find more detail about what MoD civil servants do, what they get the bonuses for, before you say this is unjustified,” Alan Johnson told GMTV.

"Our priority always has to be the soldiers at the frontline for equipment, for pay, for conditions."

Newspapers this morning quoted relatives of soldiers angry about the bonuses paid to officials. Phil Cooper - whose son received £200,000 in compensation for injuries received in Iraq - said it was "absolutely disgusting that they can do this from the safety of their armchairs".

But civil service unions have been quick to defend civilian staff.

Jonathan Baume, general secretary of managers' union the FDA, said the criticisms were “unfair and misleading”, saying the practice was common in government departments.

“We are talking about tens of thousands of people working very hard to support our troops,” Baume said. “Many of these payments are made to people serving alongside the military - in Iraq and Afghanistan. They include a very wide range of technical and professional staff.”

He added: "The payments themselves are not bonuses in the way that most people would understand them. They are non-pensionable, are not carried forward to the next year and are taken out of the overall pay pot set by ministers. This means that over recent years pay levels for civil servants in the MoD have been depressed."

PCS general secretary Mark Serwotka said the average bonus for MoD staff in his union was between £400 and £500.

“They will feel let down at being misrepresented in an attempt to score political points and create a false divide between them and their colleagues in armed forces,” Serwotka added.

“Faced with 25,000 job cuts civilian staff in the MoD are doing a vital job in supporting the military here in the UK and in Afghanistan and Iraq.”

An MoD spokesman said: "These pay awards are met from within salary budget and have no impact on the operational or equipment budget."

"Pay awards were given to around 50,000 civil servants resulting in an average payment of less than £1,000."

But shadow defence secretary Liam Fox said the revelations would "only increase the view that the armed forces and the MoD administration are hugely out of balance."

Liberal Democrat defence spokesman Nick Harvey said the payment of bonuses when troops were short of "vital equipment" was "scandalous".