Fianna Fáil TD Darragh O'Brien has said that the former party TD, Jim Glennon, should not have issued a character reference for Daniel Ramamoorthy.
Ramamoorthy was a former government adviser who was convicted of the sexual exploitation of a 13-year-old boy in 2017.
He was given a character reference by Mr Glennon.
Mr O'Brien said that it was a bad mistake that Mr Glennon has now acknowledged and apologised for.
Mr Glennon confirmed over the weekend that he submitted the character reference for Ramamoorthy.
Last week, Ramamoorthy lost an appeal against the severity of a two years and four months' sentence imposed on him in March last year.
In a statement issued by a PR company, Mr Glennon said that it had been "an error of judgement" to write the reference and he offered an "unreserved apology to the victim and to their family" if he had added to their pain and distress.
Mr O'Brien said today that Mr Glennon has been out of politics for a long time and did not know on what basis he provided the reference for.
"No one should be providing any type of reference for sex offenders or anyone in that space. I don't believe it's appropriate," Mr O'Brien said.
Meanwhile, the online safety co-ordinator with the Children's Rights Alliance said there must be recognition of the effect on victims of character references which are offered to courts on behalf of defendants.
Speaking on RTÉ's Morning Ireland, Noeline Blackwell said what Mr Glennon knew when he was writing the reference is hard to know because it does seem that sometimes people hand these character references over "when they are asked to by a buddy".
However, she added, there must be recognition of what these references do to the victims.
"The only people who are asked to give character references are people who are seen as upstanding in the community, and they're to speak to the respectability of the person they're giving the reference about.
"That does not take into account the difficulty it is for somebody [the victim] to actually go and give evidence of this kind and go through a whole cruel trial."
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Ms Blackwell pointed out that the law has changed recently to say that in some sexual offences cases, a person giving a character reference must give it on oath or in person in court.
She explained that by the time a character reference comes up in court, a person has already been convicted of the crime.
"The character reference is that peculiar thing that just says, 'this is a respectable person'. And what Judge [John] Edwards was saying is that didn't tie in with the references that he saw, many of them, and that it didn't tie in to the vile nature of the crime," added Ms Blackwell.
At Ramamoorthy's initial appeal hearing recently, Judge Edwards had said one of the testimonials handed in on his behalf was from a TD and that it was "quite extraordinary" that he and others failed to mention the victim or the "vile nature" of the crime in their references.
Mr Glennon was a Fianna Fáil TD for the old Dublin North constituency between 2002 and 2007, having previously served in the Seanad between 2000 and 2002 on the Industrial and Commercial Panel.
It is understood he has not been a member of Fianna Fáil for over a decade.
