Fianna Fáil's Eamon Ó Cuiv has defended writing a letter to the Irish Prison Service to make representations on behalf of a drug dealer who had killed an associate.
The case, involving a man who was convicted of manslaughter, was revealed by the Irish Independent today after a freedom of information request.
Mr Ó Cuiv requested the prison service inform him when a decision was made about a request by the inmate to be moved from a high-security prison to Shelton Abbey open prison in 2012.
Today, Mr Ó Cuiv said he believed absolutely that politicians should not interfere in judicial matters.
The question of how a sentence was executed was not a judicial matter, he said.
The prison system was effectively run by the Executive, not the judiciary system, he added.
Mr Ó Cuiv said the correspondence related to someone who was at the tail-end of his sentence and there were family issues involved.
He said he had been involved in prisoner issues for 20 years.