They will call for Sir Nicholas Lyell, the Attorney General, to halt the investigation into claims that British troops murdered surrendering Argentinian soldiers.
The debate will have the air of a last-ditch stand about it as the inquiry continues and fears grow in the armed forces that prosecutions will be brought. Defendants would be the first British soldiers to be charged with war crimes.
In recent weeks there has been an unprecedented campaign uniting the military establishment, senior politicians and some newspapers to stop an inquiry which they feel will damage the reputation of the armed forces without serving the interests of justice.
The roll call of peers calling for the Attorney General to intervene includes Field Marshal Lord Bramall, who won the Military Cross in the Second World War and was Chief of the General Staff from 1979-82. He has visited the Falklands and during the debate will describe the battle for Mount Longdon, when the killings are alleged to have taken place. He will also explain the pressures which affect soldiers during combat.
Backing him will be Marshal of the RAF Lord Craig, who as Chief of the Defence Staff from 1988- 1991 commanded Britain's armed forces during the Gulf war. The Royal Navy will be represented by Lord Mottistone, who served in the Atlantic and the Mediterranean in the Second World War.
Lord Chalfont, a former soldier and defence correspondent, who has written books on military history, will support their call. The moral case for dropping the investigation will be outlined by the Bishop of Guildford, the Rt Rev Michael Adie.
The man behind the motion, which because of the constitutional limitations on the House of Lords can only advise the Government to ask the Attorney General to step in, is Lord Campbell of Alloway, a Conservative peer.
He has personal experience of the treatment which prisoners of war receive. In 1940, as a Second Lieutenant in the Royal Artillery, he was taken prisoner in France and spent five years in Colditz prisoner of war camp.
The motion is to be debated despite a statement by Lord Mackay of Clashfern, the Lord Chancellor, in the Lords last week that the Government will not stop the inquiry. However, he left one loophole open which opponents of the investigation have seized on.
He told the House that when the police investigation is completed the report will be sent to Barbara Mills, the Director of Public Prosecutions. But he added: 'The ultimate decision is one taken under the superintendence of the Attorney General.'
The investigation into claims that soldiers in the 3rd Battalion the Parachute Regiment shot Argentinian prisoners of war in cold blood on Mount Longdon in 1982 was launched after the publication of a book by Vincent Bramley, a former Lance-Corporal, who fought in the battle.
The book, Excursion to Hell, described how one prisoner was shot the day after the battle and tells of a conversation Mr Bramley had with another paratrooper who told him he had been ordered to kill prisoners thought to be American mercenaries.
Malcolm Rifkind, Secretary of State for Defence, ordered an inquiry and subsequently Scotland Yard detectives were called in. They excavated graves in the Falklands and interviewed Argentinian ex-soldiers in Buenos Aires.
Those who oppose the inquiry say that in combat soldiers are subjected to stresses which no civilian, even in the worst situation, has experienced. They add that the prosecution case would depend on accounts of events more than a decade ago from former enemies. Their opponents say the British Army should be above reproach and that to allow events to go unpunished would be to adopt the morality of undisciplined militias in the former Yugoslavia.Reuse content