A report has found the Department of Justice did not deliberately withhold emails from the Disclosures Tribunal.

The investigation says there were shortcomings in the department's response to the call for information from Judge Charleton.

But it found there was no breach of any order by the tribunal over the late supply of emails which were sent in May and July of 2015.

The controversy over who knew what and when - in relation to the legal strategy against Sergeant Maurice McCabe during the O'Higgins Commission - ultimately led to the resignation of Frances Fitzgerald as Tánaiste.