Sinn Fein is gripped by a fresh crisis, with leader Mary Lou McDonald facing accusations of a cover-up over a former Belfast Lord Mayor who sent inappropriate texts to a teenager.

As Niall Ó Donnghaile was named as the former party member at the centre of the latest scandal, Ms McDonald had to defend the decision not to reveal that he had been suspended over the messages when he quit last year.

Instead, she had publicly praised the former senator when he announced that he was standing down for “health reasons”, wishing him well for the future.

On Tuesday, it emerged Ó Donnghaile had sent “inappropriate” messages to a second person, an adult.

And within hours of Ó Donnghaile being publicly named, Laochra Loch Lao GAA club in Belfast announced he had resigned as honorary president.

It comes as Sinn Fein is engulfed in a storm after two former press officers provided references to Michael McMonagle, who was under investigation for child sex crimes.

In the Dáil, Ms McDonald had to defend Sinn Fein’s handling of a series of ongoing scandals.

The Ó Donnghaile revelations look set to spark new questions for the leadership.

On Saturday, this newspaper reported that a Sinn Fein member had resigned from the party after they allegedly sent inappropriate texts to a teenager from Northern Ireland.

The texts are believed to have been personal and physical in nature, but not sexually explicit.

Ó Donnghaile admitted his role in a statement to the Irish News, saying he had “caused great embarrassment to myself, my family, friends and former colleagues”, adding “this was never my intention”.

Ó Donnghaile, who served as Lord Mayor of Belfast between June 2011 and June 2012, stood down from the Seanad last December.

He had been a member of the Republic’s upper chamber since 2016.

But when he suddenly quit, Ms McDonald issued a statement wishing him “the very best for the future”.

She praised how he had “served diligently” and “made a valuable contribution to the Joint Oireachtas Committee on the Implementation of the Good Friday Agreement”.

DUP leader Gavin Robinson said: “When Niall Ó Donnghaile stepped down, he did so for health reasons.

“Mary Lou wished him well. SF enabled a graceful departure.

“They knew the real reason. The contempt and apparent cover-up continues.”

In the Assembly, the DUP’s Jonathan Buckley requested that First Minister Michelle O’Neill answer questions on what she knew about the Ó Donnghaile case, claiming it was “another serious safeguarding issue”.

Ulster Unionist deputy leader Robbie Butler also said that answers were needed.

“This latest set of revelations only enhance the importance of getting answers to the many unanswered questions facing Sinn Fein,” he said.

“At this point, it is inconceivable not to expect the First Minister to address the Assembly to provide the clarity that has been, so far, missing.”

Tánaiste Micheál Martin said the Ó Donnghaile revelations raised “fundamental questions” about Sinn Fein’s governance.

He said: “It appears the Oireachtas was misled on the full reasons for Senator Niall Ó Donnghaile’s resignation, following actions which the party itself described as ‘unacceptable’.

“The party’s track record of concealment and secrecy is shocking. We have seen it before in the shameful treatment of Máiría Cahill, Paudie McGahon, the cover-up over Liam Adams, and the handling of senior press officer Michael McMonagle.

“It is apparent when it comes to Sinn Fein, the party always comes first.

“It is clear Sinn Fein again failed to tell the truth on a very serious matter and seem to have been involved in a very elaborate cover-up.”

In the Dáil, Ms McDonald said procedures were initiated against Ó Donnghaile on September 12 last year and the police were informed.

She said the party was subsequently informed that a second person, an adult, received “inappropriate” text messages from the 39-year-old.

Ms McDonald defended not naming Ó Donnghaile at the time, citing health concerns, with the party told the former senator was suffering from a mental health crisis and was deemed medically unfit to work.

She said the PSNI informed Sinn Fein that the teenager was “content” with the actions taken by the party in response to a complaint about Ó Donnghaile.

She said no formal investigation followed and added: “There was no finding of illegality and no criminal charges were pursued.

“However, Niall Ó Donnghaile’s actions were not acceptable. This was made clear to Niall Ó Donnghaile at a meeting on October 5 [2023].”

She added: “Niall Ó Donnghaile stated that he would be resigning both from the Seanad and the party.”

Ms McDonald said Sinn Fein’s actions were “firstly guided by concern for the young person at the centre of this incident”, as well as accountability for Ó Donnghaile.

“He faced those consequences, ones that were proportionate to his unacceptable behaviour,” she said.

Ms McDonald said there was “nothing more important than protecting the safety and wellbeing of children” as she defended her party’s “robust disciplinary procedures”.

Laochra Loch Lao GAA club said Ó Donnghaile had resigned as honorary president of the club.

It added: “It was an ambassadorial role and he never had any contact with children or vulnerable groups.

“The club will be making no further statement.”

Separately, Ms McDonald reiterated her belief that the party “acted entirely properly” in suspending McMonagle, their former press officer, who was under investigation for sex crimes.

She apologised to the British Heart Foundation for “being dragged into this controversy” after it emerged that two other party press officers, Seán Mag Uidhir and Caolán McGinley, provided references to McMonagle. Both recently resigned.

The Sinn Fein leader said she had initiated a “complete overhaul” of party governance procedures to correct issues and shortcomings arising from the case.

At the weekend, long-serving Sinn Fein TD Brian Stanley resigned from the party amid complaints against him following an internal inquiry.

Mr Stanley slammed the inquiry as a “type of kangaroo court” and accused members of Sinn Fein of “character assassination” against him.

Sinn Fein said a complaint against Mr Stanley and a “serious” counter-allegation were referred to Gardai.