News of the commission's unpublished report comes days after Scotland Yard sent a report of its own investigation to the Crown Prosecution Service. The Director of Public Prosecutions, Barbara Mills, is considering whether there are grounds to prosecute any British servicemen.
News of the Argentine investigation was reported in the respected Clarin daily newspaper in Buenos Aires. The newspaper said the inquiry report included testimony from at least four Argentine soldiers involved in the battle for Mt Longdon in June 1982. Former corporal Jose Carrizo said British soldiers shot him in the head after he was taken prisoner - a charge supported by another veteran, Santiago Mambrin, according to the newspaper. British medics saved Carrizo's life.
Another former soldier, Nestor Flores, said he saw British soldiers shoot a wounded, unarmed soldier called Quintana; stab to death with a bayonet another one named Gramissi; and toss a grenade into a foxhole where a soldier called Delgado lay.
Other witnesses allegedly said the British forced prisoners to retrieve unexploded cannon and mortar shells from battlegrounds. Two former soldiers were said to have told the commission that British jets dropped fragmentation bombs - banned under the Geneva convention - on Argentine positions.
No confirmation of the report was available from Argentina's defence ministry, which appointed the commission last year.
The Scotland Yard investigation was launched after claims by a former paratrooper, Vincent Bramley, in his account of the Falklands war, Excursion to Hell, published in 1991. He detailed allegations of brutal behaviour by some of his comrades, involving claims of execution of prisoners after the battle for Mt Longdon.
Some of his allegations were supported by a British officer who said he witnessed the execution of a wounded Argentinian soldier.
Labour MP Tam Dalyell, who has raised the issue in the Commons, said last night that the Clarin report should be taken seriously. 'One cannot let sleeping dogs lie any longer, if these things are being spoken of widely,' he said. 'If this is being said by serious people, we have to get to the truth. The truth may be cleansing. The truth has to be laid bare if possible.'
But senior Tory backbencher Michael Shersby, who chairs the Commonwealth Parliamentary Association Falkland Islands Group, and is an adviser to the Police Federation, said: 'I don't think any other country in the world would have gone to the extent Britain has gone to to examine those allegations. It is up to the DPP to decide whether there are grounds for prosecutions, and whether it is in the public interest or not.'
'I don't know of any reports at all of British troops using equipment which contravened the Geneva convention. That is news to me.'
He added that he had seen reports from a number of Argentine servicemen who said they did not wish to reopen the events of the war, recognising that all wars were tragedies.
The Ministry of Defence said last night that it was unaware of the latest allegations. A spokesman added: 'The point that seems to have come across generally from the Argentine soldiers involved is that they felt that the British soldiers on the whole treated them with the utmost fairness and decency.'