Sinn Fein yesterday turned down an invitation to the annual garden party at Hillsborough Castle in Co Down on Wednesday which Prince Charles will attend.
Unionist and Tory MPs had condemned the decision of the Northern Ireland Secretary, Dr Mo Mowlam, to invite the Sinn Fein president, Mr Gerry Adams, and the party's chief negotiator, Mr Martin McGuinness as "premature" and "contemptible".
The garden party is to celebrate the 50th anniversary of the British National Health Service, and all 16 Northern MPs have been invited.
The Sinn Fein chairman, Mr Mitchel McLaughlin, said Sinn Fein would not attend the party because of Prince Charles's connections with the British army and the events of Bloody Sunday.
Earlier, Dr Mowlam insisted that the two had been invited as elected MPs, but would not meet or shake hands with the royal guest. She told BBC's Breakfast with Frost that she would not have put members of the royal family "at the garden party in a position where they would meet Sinn Fein".
The UUP MP, Mr Ken Maginnis, said the Sinn Fein MPs should "stay away, at least until they are in a position to tell us that their war is over".
It is understood that Prince Charles was unhappy about the prospect of meeting the two MPs. A palace spokeswoman yesterday denied it had seen the guest list in advance.
The British Prime Minister, Mr Tony Blair, will meet the Taoiseach and the President during his visit to Dublin later today. Mr Ahern and Mr Blair will discuss Northern Ireland at a meeting at Government Buildings at 7.30 p.m., before a dinner where the forthcoming EU summit in Cardiff will be discussed.
Later the Taoiseach will accompany Mr Blair on a courtesy call to Aras an Uachtarain.