Latest: Mary Lou McDonald criticised over 'standard three months non-sanction' for senator

Update 9.58pm: The leader of the Labour Party, Brendan Howlin, says it's clear that any hope the new Sinn Féin leadership would herald the dawn of a new era has now disappeared.

It follows the suspension of Senator Máire Devine from the party, for what it calls “unacceptable twitter activity last night”.

The Senator had retweeted an offensive tweet in relation to a prison officer killed by the IRA.

“It is business as usual with Sinn Féin as another of their pubic representatives has engaged in commentary designed to inflict maximum insult on their rivals,” Howlin said.

“It really is only a question of who's next?

“It would appear that the standard three months non-sanction is not making a difference. It is clear too, that Mary Lou McDonald is going to continue to talk the talk but not walk the walk on this issue.”

Original story (2.06pm): Sinn Féin's Máire Devine suspended from party over 'unacceptable Twitter activity'

A Sinn Féin senator has been suspended for three months after retweeting an offensive tweet about the killing of prison officer Brian Stack.

Mr Stack, a chief prison officer in Portlaoise, was shot in the neck by the IRA in March 1983 and died 18 months later.

Senator Máire Devine apologised over the posting and said it was never her intention to cause distress or hurt.

Mr Stack's son Austin said she was "revictimising" him.

Mr Stack tweeted: "It really is incredible that a political representative is revictimising the son of an IRA victim.

"I had to watch my father die after he was shot by Provos. Don't lecture me on compassion after your very cruel retweet.

"Its a resigning matter - just as bad as Barry Mc Elduff."

West Tyrone MP Mr McElduff stepped aside over a social media posting about the Kingsmill shootings.

Sinn Féin national chairman Declan Kearney said: "This is unacceptable behaviour from a Sinn Fein elected representative.

"The Ard Chomhairle has suspended, with immediate effect, Senator Devine from party membership and all party activities for a period of three months.

"The whip has been removed and Senator Devine will be outside of the Leinster House team for that period.

"Sinn Féin strongly disapproves of what has happened. There can be no excuse for the hurt and offence which has been caused to the Stack family."

It was not until 2013 that the IRA admitted responsibility for Mr Stack's murder, the only prison officer murdered in the Republic during the Troubles.

He was left paralysed and brain-damaged by the shooting as he crossed a road outside the National Stadium in Dublin in late March 1983.

He suffered for 18 months before dying from his injuries at the age of 47.

Senator Devine said: "It was never my intention to cause any distress or hurt, particularly to victims of the conflict.

"I want to offer my most sincere apologies to the family of the late Brian Stack.

"I accept the decision by the party national chairperson to suspend my membership of Sinn Féin for three months.

"I deeply regret what has happened, and want to profusely apologise for all the offence and hurt caused by my twitter activity."

She is a mental health nurse and trade unionist from Dublin and has been a member of South Dublin County Council.

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