Taoiseach Enda Kenny said no instruction had been given to Minister for the Arts Heather Humphreys about appointing John McNulty to the board of the Irish Museum of Modern Art (Imma).

Mr Kenny said the Minister did not have to inform him of every appointment made to every board.

“I am not informed of every individual appointment made for non-remunerated positions on State boards, where there are thousands of positions to be filled over the years,” he said.

“However, from now on all of that process will be removed from politics and politicians and all positions will be publicly advertised and externally verified.”

Mr Kenny said Mr McNulty had not raised any question of being appointed to a cultural board when the two discussed his possible nomination for the Seanad byelection.

"He did so, later on, when the Fine Gael personnel were dealing with the preparation of his CV," he added. Mr Kenny said he was sorry if he had confused the Opposition on the issue.

The Taoiseach was replying to Fianna Fáil leader Micheál Martin and Sinn Féin president Gerry Adams who accused him of not answering questions on the controversy.

Earlier, Mr Kenny said he had discussed the operation of the Seanad with Mr McNulty and his capacity to be a good Senator.

The Minister read his qualifications, read his credentials and appointed him, as she was entitled to do, to be a member of the board of Imma.

"He did not know at the time he was appointed whether he was going to be a candidate for the Senate or not," said the Taoiseach.

He said that when he gave his imprimatur that Mr McNulty should be considered for a nomination to contest the byelection, the Fine Gael system of validating candidates took over. A sub-committee of the party’s executive council considered the names for a nomination; 29 people were being considered and Mr McNulty indicated he would like to serve on a cultural board.

Mr Kenny added that the Fine Gael official dealing with the matter did not go back to the sub-committee, which was a cause of great “angst and a cause of concern’’ to him.

Amid heated exchanges, Mr Kenny said it was time to move on. The process of appointing to State boards was flawed and was going to be fixed.

Mr Martin said the Taoiseach's attempt in the House on Tuesday to bring clarity to the matter did not succeed and had raised far more questions than answers. "There has been a lack of clarity," he added.

He asked why Ms Humphreys would not come before the House and make a comprehensive statement on the issue.

“Why did she act with such haste in increasing the size of the board to facilitate his appointment, rather than just wait for a casual vacancy to arise and then fill it in the normal way?” he added.

Mr Adams said that often when the Taoiseach was asked a question in the Dáil he responded by saying the issue was complex as if it was beyond the comprehension "of us mere mortals on this side of the House''.

He added that he had asked the Taoiseach questions which he had ignored.