NORTHERN Ireland's police ombudsman is to formally investigate if detectives did not properly examine whether Sinn Fein president Gerry Adams covered up the crimes of his sex abuser brother.
Confirmation from ombudsman Michael Maguire's office that an investigation has been launched comes a day after senior members of the Democratic Unionist Party lodged an official complaint about the matter.
The DUP representatives asked the watchdog to examine how the Police Service of Northern Ireland (PSNI) handled the republican leader's apparent failure to alert police to his brother Liam's abuse when he first learned of it.
PSNI officers made a recommendation to the Public Prosecution Service (PPS) that no prosecution be taken against the Sinn Fein veteran.
Mr Adams has been facing mounting criticism over what he told police about his paedophile brother and when.
But he has insisted that he committed no offence and has accused political rivals of exploiting a family issue to attack him.
Liam Adams was found guilty last week of a series of rape attacks on his daughter Aine in the 1970s.
During a first trial earlier this year, which ultimately collapsed, the Sinn Fein leader, now a TD in the Irish Republic, claimed he first heard of the sex abuse claims in 1987 and, 13 years later, his younger brother admitted his guilt to him.
The high profile republican has been criticised for not informing the police at the time of the revelations, with his statements to detectives not coming until 2007 and 2009.
The PSNI, which recommended no prosecution against Gerry Adams before his brother's trials began, has pledged to re-examine all the evidence relating to the case in light of the Sinn Fein leader's testimony in the witness box.
Northern Ireland's Director of Public Prosecutions, Barra McGrory QC, has already announced that the region's Attorney General, John Larkin QC, is to examine the role of prosecutors.
Informed by the PSNI recommendation, the Public Prosecution Service (PPS) decided not to take any action against Gerry Adams.
A spokesman for the Police Ombudsman said a formal investigation had been launched into the complaint. He said the office's head of investigations was examining how the probe should proceed.
DUP chair of Stormont's justice committee Paul Givan, who was one of those who lodged the complaint, welcomed the move.
"Serious questions need to be addressed in respect of what actions were taken - or, in this case, not taken - by the PSNI after reviewing a witness statement made in 2009 by Gerry Adams to establish if a criminal offence had been committed," he said.
"I am disappointed the Chief Constable (Matt Baggott) declined the opportunity to invite the Ombudsman to carry out this investigation."
Mr Givan also called for an independent panel to be appointed to oversee the PSNI's review of the case to ensure that the exercise commanded public confidence.
Yesterday, Mr Adams, a former MP for West Belfast but now TD for Louth, reiterated his view that he had done nothing wrong.
"I know I committed no offence and I know I did what I considered to be the right thing, and I co-operated fully with the PSNI, with the PPS, with the courts," he said.
"I gave evidence in the courts. So I don't have any concerns about that."
Mr Adams did not give evidence at his brother's second trial, which ended with his conviction last week. Liam Adams, 58, is due to be sentenced next month.
Taking to the witness box in the first trial, which collapsed due to legal reasons, the Sinn Fein leader told Belfast Crown Court he first confronted his brother when they met in Buncrana, Co Donegal, in 1987 and that he had denied the abuse.
He then claimed that his brother later confessed while they were out walking together in the rain in Dundalk, Co Louth, in 2000.
Aine Adams, who has waived her right to anonymity, initially reported the abuse to police in 1987 but did not pursue a prosecution as she believed detectives were more concerned with gathering information on Gerry Adams and other members of their family.
It would be another 20 years before she again asked the police to get involved.
The review by Mr Larkin into the PPS's role is expected to last two weeks.