A Sinn Féin Senator has formally apologised to the family of Brian Stack in the Seanad following comments she made on Twitter in relation to the prison officer, who was killed by the IRA.

"I want to put on the record my most sincere apologies to the family of the late Brian Stack," Máire Devine said.

Ms Devine said she retweeted what she thought was a genuine tweet without having read the full content of the tweet.

The tweet in question used an offensive phrase to describe the former prison officer at Portlaoise Prison.

"A number of follow up tweets from me where wholly inappropriate and I deeply regret that. I want to again apologise for any and all offence and hurt that was caused by my twitter activity. It was never my intention to cause any more hurt to those already in deep distress," Ms Devine added.

The Senator was suspended from Sinn Féin for three months following what the party described as "unacceptable twitter activity" on Sunday 18 March.

Party leader Mary Lou McDonald said she wanted to sincerely apologise to the Stack family following the incident.