By Michael White The Government last night rounded off a day of spectacular military and diplomatic humiliation with the public admission by the Foreign Secretary, Lord Carrington, and the Defence Secretary, Mr John Nott, that Argentina had indeed captured Port Stanley while the British Navy lay too far away to prevent it. At a defensive and unhappy press conference in the Foreign Office Ñ itself a rare event Ñ Mr Nott denied as Òridiculous and quite untrueÓ rumours at Westminster that he had offered his resignation to Mrs Thatcher, and Lord Carrington rejected with a shake of his head any suggestion that he might resign. But the irony of a government elected to strengthen BritainÕs defence posture of finding itself in this position will not be lost on MPs and some were saying last night that the debacle in the Falkland Islands was the GovernmentÕs most dramatic single humiliation. The growing anger of Opposition MPs Ñ which increased through the continuing uncertainty Ñ will now be joined by Tory backbenchers who have been holding off in recent days. The government business managers were warned before the invasion that a few Tories were threatening to resign the whip if things went wrong. The belated confirmation of the invasion which had apparently eluded ministers Ñ though not the worldÕs media, American intelligence, or radio hams Ñ came shortly after it had been agreed that the Prime Minister herself would open a three-hour debate on the Falkland crisis in the first Saturday sitting of the Commons since the abortive Suez invasion of 1956. Tory MPs had been privately assured that British troops would open fire and that the Navy was on its way. But in the first of yesterdayÕs two Commons statements Mr Humphrey Atkins, the deputy Foreign Secretary, had Ñ to the annoyance of some Tories Ñ stuck to an earlier ministerial formula that Britain would defend the islands Òto the best of our abilityÓ. Last night, Mr Nott still could not say if the 84 Marines at Port Stanley had resisted the invasion. But he did say: ÒThe British never give orders to anyone to surrender,Ó and that he assumed Òthat any member of the British armed forces do not surrender.Ó Some Conservatives believe that if there had been no fighting it would inhibit BritainÕs ability to counter-attack. Former Labour ministers, including Mr Callaghan, Mr John Silkin and Dr David Owen, are convinced that it was the discreet stationing of a naval force over the horizon which led the Argentinians to back off in 1977 Ñ a comparison derided last night by Lord Carrington. Mr Silkin told MPs that in LabourÕs view the Government had been taken unawares, that its preoccupation with Trident instead of with the NavyÕs need for surface ships had weakened its military hand and its imminent withdrawal of HMS Endurance from the area had given the Argentinians the wrong impression Ñ points which were later echoed by Mr David Steel, the Liberal leader. It was Dr Owen, the Labour Foreign Secretary in 1977 and now an SDP leader, speaking in a radio interview, who likened the crisis to Suez if not to BritainÕs humiliation when the Dutch raided the Medway towns in the 1660s. Dr Owen was expected to call for a special commission of inquiry along the lines of the inquest into the disaster at the Dardanelles in 1915. TodayÕs debate, which will be opened by Mr Foot and Mrs Thatcher and wound up by Mr Nott and Mr Silkin is likely to prove a rough ride for the Defence Secretary, whose future can by no means be secure. At last nightÕs press conference he confirmed that the Navy had been put on immediate notice for operations and that a substantial task force sufficient to meet the Argentine invasion had been put on readiness for operations and was in preparation at this moment. ÒIt has not yet been given order to sail,Ó he said. Mr Nott said that the arrival of the scrap merchants on South Georgia Ñ Ò12 people with a valid salvage licenceÓ Ñ was not sufficient reason in itself for sending such a task force. Coupled with Lord CarringtonÕs insistence that military manoeuvres might produce the very excuse for military action which the Argentinians wanted, this view is likely to baffle MPs who were complaining last night of an intelligence failure by the Foreign Office and a lack of liaison between the FO and the Defence ministry. During the day, Conservative MPs were increasingly bellicose in private about the need to take on the Argentine Navy. And despite the constant reiteration last night of the logistical problems involved across 8,000 miles of ocean, Mr Nott rounded off the press conference by saying that people Òshould not conclude that we do not have the military capacity to deal with a problem of this kind Ñ on a sustained basis.Ó Government spokesmen had been laying great stress during the early part of the day upon the moral condemnation coming from the United Nations, and Lord Carrington himself twice resorted last night to Mr AtkinsÕs formula in the Commons that Òwe are taking appropriate military and diplomatic measures to assert our rights under international law.Ó