The Minister for Defence, Michael Smith, has announced that an army lieutenant dismissed 33 years ago was properly dismissed despite recent allegations to the contrary.
In a statement, the Department said the inquiry failed to uncover any evidence to sustain the allegations about the dismissal of Donal De Roiste.
Mr de Roiste is a brother of former Presidential election candidate Adi Roche.
The family said that they will carefully consider the report and will issue their response next week.
Mr De Roiste and his family launched a campaign in July this year, aimed at clearing his name.
The former army lieutenant said he was never given a reason for his dismissal. He alleged that it centred around a car accident in 1967 in which he was a passenger and his subsequent refusal to support a senior army officer in a civil case surrounding the accident.
The Department of Defence has now released the report into the circumstances surrounding his dismissal. The army said it had failed to uncover any objective evidence to sustain the range of allegations made by Mr de Roiste.
The report said army records showed no link between a car accident and his dismissal. It said he had been made fully aware of the circumstances surrounding his retirement.
It said army intelligence officers had taken a serious view of sightings of Lieutenant de Roiste in the company of members of an IRA splinter group. It also concluded that his position as Lieutenant would constitute a grave security risk.
Mr de Roiste's family said claims that he had been involved in subversive activity were "ludicrous".
His sister, Adi Roche, said her brother frequented pubs and sang ballads with his friends, like many people at the time.
She said the family looked forward to finally getting access to her brother's files and clearing his name.