The Ceann Comhairle of the Dáil, Seán Ó Fearghaíl, has said he believes that Sinn Féin TD Brian Stanley needs to give a "credible political response" to his controversial weekend tweet about the 1920 Kilmichael ambush and the 1979 Warrenpoint bombings.
Replying to a letter of complaint by Northern Ireland First Minister Arlene Foster, Mr Ó Fearghaíl said he was "personally appalled and profoundly dismayed" by the contents of the tweet.
He told Ms Foster: "To post such a hurtful statement on social media is not only highly disrespectful to victims and their families, but an affront to all those committed to democratic politics on the island of Ireland."
The Ceann Comhairle wrote that Mr Stanley's response should be one which "sincerely acknowledges the hurt and offence caused to the families who lost loved ones in Narrow Water, as well as the hurt and offence caused to those who suffered grievously during the 30 years of violence in Northern Ireland".
He told the DUP leader that he knew Mr Stanley to be "an experienced and fair-minded member of Dáil Éireann".
However, he added that: "I believe that it would be in keeping with the values and standards that we all hold dearly, particularly reconciliation and mutual respect, if the matter were to be more properly addressed at the earliest opportunity."
Mr Stanley is due to chair a meeting of the Dáil's Public Accounts Committee tomorrow.
Mr Ó Fearghaíl said he had given the matter "very careful consideration" and while he was "particularly conscious of the independent and non-partisan nature" of his office, he felt that "there is a duty on us all to uphold the fundamental values and standards that are the cornerstones of democratic politics".
The Ceann Comhairle indicated that disciplinary measures would not be required if such an apology was made when he said: "In such circumstances, it would not be necessary to consider other actions."
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A Sinn Féin spokesperson said tonight: "Brian Stanley has apologised for, and deleted, the insensitive and inappropriate tweet."
They added that the Laois Offaly TD will "make a statement to the Public Accounts Committee at its meeting tomorrow".
Earlier today, Sinn Féin leader Mary Lou McDonald said that Mr Stanley will not be disciplined further after posting what she called "a clumsy and ill-judged tweet" relating to the Kilmichael ambush and the Warrenpoint bombings.
Speaking to RTÉ's Morning Ireland, Ms McDonald said Mr Stanley acted quickly to remove the tweet and is very apologetic and understands fully that the tweet was ill-judged.
However, she said she would not remove him from his role as chairman of the Public Accounts Committee (PAC), but he would address the controversy with his committee colleagues when they meet tomorrow.
Ms McDonald apologised universally to people who "like me wish to forge a constructive path ahead and for whom the tweet jarred as it goes against the challenging proposition of recalling history and to do it mindful of others".
She added that "unfortunately Brian's tweet did not contribute to that, but he has apologised and I'm happy it won't happen again".
Ms McDonald said Mr Stanley is a "very effective and even-handed chair" of the PAC and the work is essential "and he is anxious to continue and I am too".