Taoiseach Enda Kenny has accused Fianna Fáil justice spokesman Niall Collins of "seeking to influence" a judge's decision by sending a letter asking that a drug dealer not be jailed.

Mr Kenny described the matter as “very serious”.

“I think this constitutes direct intervention in the administration of justice,” he told reporters in Dublin today.

“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 Micheal Martin. "It is not good enough to say that the matter has to wait until sentence is finally passed in October," Mr Kenny added.

“It is a matter for the judge to have done that and he should not have been sought to be influenced directly by the intervention of a public representative, particularly a public representative carrying the responsibility of a shadow ministry for justice.”

In response, Mr Martin said: “Niall Collins has issued a statement explaining his involvement in this case. I have also spoken to him. He is absolutely clear on the importance of an independent judiciary.

“As a basic principle, I do not believe that Oireachtas members should involve themselves in criminal proceedings.

“In this case, where there are exceptional circumstances, Niall Collins has not sought to question the validity of the conviction, and respects absolutely the independence of the sentencing judge.

“I understand that in this exceptional case, Niall Collins was acting only on the grounds of compassion for four young children who have already lost one parent in tragic circumstances earlier this year.”

Meanwhile, in a statement this afternoon Mr Collins said he wrote to the judge in the case because the convicted man’s children had “lost their mother through suicide”.

Mr Collins said he would have preferred to avoid commenting until the case was concluded, but the level of public and media interest in his action had been considerable, and understandable.

“To be very clear, I wrote the letter outlining the exceptional circumstances of this family as the four children lost their mother through suicide earlier this year and I truly believed that the judge should be made aware of these tragic circumstances so that they could be taken into consideration when sentencing,” he said.

“My decision was based solely on compassion and concern for the four children. Sentencing in this case has been deferred until October and I do not intend to speak about it any further.”

Mr Collins said he regretted if his actions appeared to suggest he did not respect judicial independence.

“I fully understand and respect the absolute independence of any sentencing judge in making their decision based on the facts put before them during any trial. If my actions suggest anything other than total respect for judicial independence that is a source of genuine regret,” he said.

Independent TD Lucinda Creighton had called Mr Martin to take action against Mr Collins.

She said Mr Collins’s decision to write to the judge asking him not to jail a convicted drug dealer was a “huge lapse of judgement”.

“I think it’s completely wrong. He shouldn’t have done it and I think Micheál Martin should take action,” she said.

“Given his particular role, and he has been a very effective voice on the GSOC issue and a range of issues, I was really surprised and think it’s a huge lapse of judgement.”

Fianna Fáil TD Billy Kelleher had earlier defended his party colleague’s decision to write to the judge.

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 handwritten letter was presented by lawyers representing a 40-year-old father of four from Co Limerick.

Earlier this year, Hugo Porter of St Patrick’s Villa’s, Castleconnell, Co Limerick, pleaded guilty to possession of cannabis and cannabis resin for the purpose of sale or supply.

At Porter’s sentencing hearing on Monday, the judge was told the convicted man was the sole carer of his four young children as his wife had died in tragic circumstances earlier this year.

Defence counsel Michael Collins argued that the family circumstances of the accused man placed the case in the “exceptional category”.

He said this was supported by the letter written by Deputy Collins, which was presented to the judge.

Prosecution counsel John O’Sullivan urged the judge “not to attach too much weight” to the letter.

He said the practice of public representatives writing to sentencing judges was “not uncommon” in the recent past but that it was no longer commonplace.