Fianna Fáil leader Micheál Martin has strongly backed his party's justice spokesman Niall Collins and called for the formulation of a code of conduct stating politicians should never intervene in judicial matters.

Mr Martin said Mr Collins was a young politician with a future and would retain his position despite the controversy.

“I’ve made it clear that as a basic principle politicians should not be involved in criminal cases in the courts, even at the sentencing stage. The motivation here was a very genuine one,” Mr Martin said.

Speaking to RTÉ, Mr Martin said Mr Collins was "obviously very concerned about vulnerable children who could end up in a parentless situation". He said Mr Collins's motivation was genuine.

“He accepts that it was a wrong intervention and he’s not going to do it again,” Mr Martin said.

“He’s not the first politician to have done this. In that context, many politicians in the past who wrote such letters are in Government today and I think have moved on,” he added.

“His position is tenable...He’s a young politician and he has a future ahead of him. He will have learned lessons from this experience.”

Mr Martin said such a mistake should not end someone’s tenure in a particular position. “Into the future he’ll continue as our justice spokesman,” he confirmed.

Asked if he thought there should be a code of conduct to clarify the situation, Mr Martin said a previous cross-party effort to formulate such a code had “withered on the vine”.

He said: “I would accept that there should be a code...collectively all political parties should reengage with a view to developing a code.”

Mr Collins has said he made a mistake in writing to a court seeking leniency for a convicted drug dealer.

The Limerick TD said he thought it was appropriate for him to remain as his party’s justice spokesman.

“I’ve been very upfront. I’ve said I won’t do it again. It was a mistake to do it. I’m sorry it worked out the way it did,” he said.

Mr Collins said the Fianna Fáil leader had asked him not to engage in such a practice again.

Asked by Sean O’Rourke on RTÉ Radio One if he thought it was appropriate for him to continue as justice spokesman, he replied: “I think so.”

Mr Collins emphasised the “tragic circumstances” of the convicted drug dealer’s children whose mother had died by suicide.

He said he was particularly struck by the circumstances and was asked to present the facts to the court by people close to the family.

There was no political gain for him as the family were from outside his constituency.

However, he said he would not do it again. “It shouldn’t be done. I for one won’t be doing it again.”

Earlier he had faced renewed criticism as Minister for Jobs, Enterprise and Innovation Richard Bruton joined Taoiseach Enda Kenny and Tánaiste Eamon Gilmore in criticising Mr Collins, saying that the independence of the judiciary had to be respected.

“Every politician understands, or should understand, the fundamental independence of the judiciary and the political system.

“It’s something that is hard-wired into us and more especially a justice spokesman should understand that,” Mr Bruton said.

“This was something totally inappropriate for Niall to have done and I think it clearly is a serious matter and he needs to sort that out.”

“Where you cross the line is where you seek to contact a Judge about leniency for a convicted drug dealer. You are crossing a line that every politician should understand that that’s a line you cannot cross.

“We have to respect that fundamental independence. If the boot was on the other foot I know what Fianna Fáil would be saying,” he said.

“You do not get involved in judges making decisions about the leniency or the conviction of people,” he told RTÉ’s Morning Ireland programme.

Mr Collins had defended his decision to write to a court, arguing there were “exceptional circumstances” in the particular case.

This morning Fianna Fail TD John McGuinness came to Mr Collins’s defence and accused Taoiseach Enda Kenny of going over the over the top in his reaction to Mr Collins’s letter.

Mr Kenny said yesterday the matter constituted a direct intervention in the administration of justice, an observation which Mr McGuinness described today as incorrect.

“He (Mr Kenny) has gone over the top. He said it was direct intervention in the course of justice, when in fact it isn’t.

“It was a simple letter emphasising the circumstances of the family as far as I understand it,” Mr McGuinness told the Irish Times this morning, adding that he has not seen the letter.

“To start jumping up and down about resigning is a bit much when there’s so much else going on,” Mr McGuinness said.

After initially making no comment, Mr Collins was left with little alternative but to respond yesterday after the disclosure of the letter led to widespread condemnation from all other political parties.

As the Taoiseach accused him of trying to influence the court and the Tánaiste said it was inappropriate for Mr Collins given that he was justice spokesman for the party, Mr Collins argued that there were “exceptional circumstances” in the particular case.

He had been compelled to write because the drug dealer was the sole carer of four children after they lost their mother through suicide earlier this year.

The letter was presented to court during a sentencing hearing following a man’s conviction for possessing cannabis resin worth over €18,000 in 2011.

“My decision was based solely on compassion and concern for the four children,” he said.

Earlier, Mr Kenny described the matter as “very serious”. “I think this constitutes direct intervention in the administration of justice,” he said.

“I think this is an issue where not only just a public representative but a shadow minister for justice has written directly to a judge seeking to influence his decision in the administration of justice as the judge thinks fit.”

Mr Kenny called for an “immediate explanation” of the intervention from Fianna Fáil leader Micheál Martin. “It is not good enough to say that the matter has to wait until sentence is finally passed in October.”

Mr Martin responded that on principle he did not believe Oireachtas members should involve themselves in criminal proceedings. He said Mr Collins's intervention had been made because of the exceptional circumstances in this case.

The issue arose at a sitting of Limerick Circuit Criminal Court on Monday where Judge Carroll Moran was asked not to attach any weight to the letter written by the TD. The letter was presented by lawyers representing Hugo Porter (40), Castleconnell, Co Limerick. He pleaded guilty to possession of cannabis and cannabis resin for sale or supply.