Thousands of soldiers will be forced to pay back cash to MoD

Thousands more armed forces staff also had to reimburse the Ministry of Defence after almost 20,000 overpayments.

New figures released to the House of Lords revealed the blunders, which have been blamed on errors in a new system.

It comes amid criticism of sub-standard kit, accommodation and pay levels within the armed forces.

The figures show there were 50,764 underpayments and 19,546 overpayments between January and November last year.

There were a further 7,589 payments where the MoD was unable to say whether they were higher or lower than intended.

Liberal Democrat defence spokesman Nick Harvey said the government must sort out the situation "without delay".

'Life and limb'

"A handful of teething problems would be understandable, but these new figures show the scale of the problem is far worse than that, " he said.

"We ask enough of our armed forces already without burdening them with needless financial difficulties.

"The government must get this sorted out without delay. Day in, day out our armed forces risk life and limb for their country."

While shadow defence secretary Liam Fox branded the MoD "incompetent".

He said: "Forces personnel have enough to worry about as it is without having to check the MoD is paying them correctly.

"The contrast between the professionalism of our troops and the incompetence of the MoD grows by the day."

The disclosures follow criticism of the Joint Personnel Administration system, introduced in full last year, which centralised payments paperwork across the three forces.

In a written answer to peers, Baroness Taylor said there had been 2.4 million payments processed via the system last year.

The errors could have happened because of late and wrongful inputs although the MoD did not collect data on those incidents.

She said all pay errors would be rectified as soon as possible regardless of if they were over or underpayments.

"Armed forces personnel who have been underpaid can request cash supplements equivalent to the underpayments from their units," she said.

An MoD spokesman said there were no "systematic problems" with the Joint Personnel Administration (JPA).

He said: "Since the roll-out of JPA was completed in April last year, we have achieved an accuracy level of 99.3%.