“I’ve been told by my lawyers that these letters are subject to professional legal privilege, and I’ve been told that I cannot publish them,” he said.
Mr Norris has released a letter written to the judges of the Israeli supreme court in 1997 seeking clemency for Ezra Nawi, convicted of the statutory rape of a 15-year-old boy.
But he has refused to release other clemency letters he wrote in the same case, citing legal advice.
“The other letters are letters to lawyers, for example; they’re covered by privacy, they’re covered by legal constraints, and I cannot do that,” he told RTÉ Radio.
Responding to suggestions that he could read them in the Seanad, which is covered by privilege, he said: “Well, that’s a suggestion… I’m not a lawyer.”
He described reports that the letters could not be published because they were possibly defamatory as a “misunderstanding”.
The Star quoted barrister Muireann Noonan as saying: “We have decided these letters will not be released. There are elements that could be viewed as defamatory… The victim in this case is now a man in his late 30s… What he might read in these letters might not necessarily be defamatory, but that might not stop him from taking a defamation case.”
However, Mr Norris said this was not the issue. “No, I believe that that is a misunderstanding,” he said.
In the released letter, Mr Norris wrote that Mr Nawi had been “lured into a carefully prepared trap” and had “unwisely pleaded guilt”.
Taoiseach Enda Kenny suggested that candidates should be “upfront” with the electorate.
“The people are going to have their say about who they want to represent this country,” he said.
“From that point of view, I think that all the candidates have to be upfront with the electorate.”