Fine Gael's Seanad nominee has announced he is to step down from the IMMA board with immediate effect.

John McNulty says he is forced to step down because of IMMA's own internal rules - which forbid him from remaining as a director if he is seeking public office.

"I will continue to be a member of IMMA, and an active supporter of their work," he said.

"I look forward to continuing my election campaign, for a seat in the Seanad.”

The move comes as the political controversy over his appointment continues to grow.

This afternoon Taoiseach Enda Kenny denied giving direct orders to the arts minister Heather Humphreys, instructing him to appoint Mr McNulty to IMMA.

"I've never given instructions for ministers to make appointments," he said.

"Where ministers are making appointments to the chairs of boards or semi-states or whatever, the minister makes the nomination to cabinet.

"But obviously there are thousands of positions that are required to be filled occasionally, and obviously we've encouraged people to apply in a particular way for that.

"But ministers are free to make appointments to a particular boards."

However, the Taoiseach had been asked whether he could also deny such instructions being made from either his Department or from Fine Gael centrally, and did not respond to that question.

Asked if the timing of Mr McNulty's IMMA appointment and Seanad nomination was simply a coincidence, he said: "I'm not saying anything... I'm saying the rules that have applied here are the rules that have always applied.

"It is the responsibility of the leader of Fine Gael of the day to make the choice [of Seanad nominee], and make that decision, and that's what I did and I accept responsibility for it."

Earlier this afternoon, minister Humphreys had refused to state whether she knew Mr McNulty was being lined up for the Seanad when she appointed him to IMMA.

Heather Humphreys says she had no role in his Seanad bid - which was announced just six days after she moved him onto a state board.

The move has sparked tensions with Labour - with Tánaiste Joan Burton refusing to say whether her party will back McNulty in next month's by-election.

One of the other Seanad candidates put forward by Fine Gael's executive council, Samantha Long, has today resigned from the party in protest at the decision to overlook three female candidates in favour of Mr McNulty, 37.

- Gavan Reilly and Bernie Jameson