Major Eric Joyce was suspended 18 months ago for a series of articles and interviews in which he accused the army of snobbery and public school bias. No further disciplinary action has yet been taken.

He is now on a shortlist of approved Labour candidates for the Scottish Parliament to be established in 1999.

Eric Joyce: Criticisms "broadly in line" with Labour's agenda

Shadow Defence Secretary John Maples has written to Defence Secretary George Robertson asking about the officer's links to Labour and suggesting that ministers are "protecting" him.

He also wants to know why it has taken so long for the Army to bring action against Major Joyce, who the Tories say is guilty of "gross insubordination".

"Army officers should not be involved in matters of political controversy on either side," Mr Maples said.

"It is very important that the armed forces in general are seen to be impartial and Major Joyce has clearly breached that rule in a great many ways.

"The army shoud have taken disciplinary action. I just wonder if ministers are preventing this."

John Maples: Letter to the defence secretary

Speaking to BBC News, Major Joyce denied that his criticism of the army had the government's approval.

"It certainly doesn't have tacit approval on a day-to-day or even a month-to-month basis," he said.

"I think what I'm saying is broadly in line with the modernising agenda which the government is promoting."

The army also rejected Mr Maples' allegation and said that the major's case was undergoing the "usual rigorous procedures". There was no question of leniency for his political views.

Changing image: An Army recruitment poster

In 1997, Major Joyce was warned about his future conduct after writing an unauthorised pamphlet for the left-wing Fabian Society.

He went on to make regular media appearances and launched a magazine, the Armed Services Forum, which was authorised but contained severe criticism of the forces.

The major, who has served in Northern Ireland, Belize and Germany, described the army as being run by a coterie of white, male, privately-educated generals and said it was rife with racism and sexism.

In March this year, senior officers described Major Joyce as "unemployable", having lost the trust of his fellow officers - the recognised first step towards a discharge from the army.