The then-Prime Minister was also in no mood to meet Taoiseach Charles Haughey because of Ireland's plans to back calls for a ceasefire in the conflict off Argentina.
State documents show how Britain pressurised Ireland during one of the most critical stages of the war to abstain from a planned United Nations resolution calling for an end to military action. It believed every vote was crucial and Ireland had let it be known it was in favour of a ceasefire and would likely vote in favour of it.
An unnamed Irish diplomat at the UN attending lunch with then Foreign Secretary Francis Pym sent a cable back to Dublin warning about the threats from London.
During the lunch meeting at the start of June 1982, Mr Pym, who was appointed Foreign Secretary during the Falklands War after Lord Carrington resigned, said he deplored what had happened to Anglo-Irish relations, which he described as getting worse every day.
The deterioration in relations was particularly disappointing to Mrs Thatcher, who had accepted the "unique relationship" between the two countries, he told the Irish official.
According to the files, just released into the National Archives under the 30-year-rule, Mr Pym asked Ireland to at least abstain from a UN vote on a Panama-Spain proposed resolution to the Falklands crisis, calling for an immediate ceasefire. But the diplomat wrote: "I gave him no hope of this in light of our stand in the (security) Council and explained our policy at some length."
In the event, Britain vetoed the ceasefire resolution and two days later the Versailles summit supported the British position.