RTÉ Director General Noel Curran has said the review into the Frontine Presidential debate published two weeks ago was difficult reading.
Mr Curran told the Joint Committee on Transport and Communications that following the upholding of complaints, he expressed RTÉ's deep regret and apologised on behalf of the station to Seán Gallagher.
He said the very serious editorial failures had rightly caused RTÉ to review all of its editorial practices.
He also said that given the thousands of editorial judgements RTÉ makes, there will be mistakes. However, he said RTÉ would learn from those mistakes.
Mr Curran outlined a lengthy series of changes to Current Affairs programming, including new appointments and a new process for dealing with serious editorial complaints.
He said all of the changes made were just steps in the right direction, but they clearly showed determination to make RTÉ journalism stronger, fairer and more transparent.
Mr Curran said he was fully aware of the significant changes made to strengthen journalism will mean little unless acted on by all management and editorial staff.
He said that all staff shared a responsibility to regain trust of the audience.
Fianna Fáil Senator Ned O'Sullivan said there still remained a lingering doubt or suspicion amongst the public that there was an agenda on the night of the programme.
He said he did not think it was right of the report to conclude there was no bias.
He said the softness of the approach to Michael D Higgins was remarkable and his left wing views or his views on abortion were not put to him.
Mr Curran said he had not said the Frontline programme did not have an impact on the election, but he did not know how anyone could make the judgement that it decided the outcome of the election given the range of other appearances that happened over those two days.
He said he did not believe the debate alone determined the outcome.
On the issue of the second tweet, Mr Curran said it was not put to the executive producer or to the presenter to correct it and they were unaware of it on the night.
Fianna Fáil's Michael Moynihan said he was surprised that presenters were "such robotic".
Mr Curran said presenters were not robotic and they could make adjustments.
He said they could follow through with supplementary questions and it was not that every question a presenter was asked was given to them.