A spokesman for Fine Gael's presidential candidate has said it is his understanding that Gay Mitchell, over his more than three decades in politics, has made pleas for clemency on behalf of members of the public.

However, the spokesman said that Mr Mitchell is not currently in a position to specifically identify the number, nature or outcome of those pleas, or the jurisdictions where they were made.

The statement comes as it emerged Mr Mitchell made an appeal for clemency in 2003 in an effort to prevent a double killer being given a lethal injection in the US state of Florida.

Paul Hill, an anti-abortion fanatic, was sentenced to death after murdering a doctor and his bodyguard outside a Florida abortion clinic in 1994.

Mr Mitchell wrote to then Florida governor, Jeb Bush, arguing that while the crime was senseless, putting Mr Hill to death would only perpetuate the cycle of taking life.

However, his plea was ultimately ignored and Mr Hill was put to death.

Today, Mr Mitchell's spokesman said his plea was that the death sentence be commuted to life or a lengthy sentence, and was based on his implacable opposition to the death penalty.

The spokesman said he understands that there were other pleas for clemency made by Mr Mitchell during his time in politics, but at present Mr Mitchell was not in a position to give further details.

A spokesman for Labour's candidate Michael D Higgins said he has never written to a judge in relation to any criminal matter.

The two independent candidates for the presidency, Mary Davis and Sean Gallagher, have both said they have never sought clemency for anyone facing or convicted of criminal charges.