Presidential hopeful Sean Gallagher has claimed the RTÉ Frontline debate "changed the outcome of the presidential election" in 2011.
The entrepreneur, who finished runner-up to Michael D Higgins seven years ago, apologised to councillors in Leitrim for how he handled himself during the debate.
And speaking publicly about the controversy for the first time, he said he felt "compelled to hold RTÉ accountable" for the "very serious breaches" of the Broadcasting Act.
Mr Gallagher sued RTÉ for damages over the ‘Tweetgate’ incident. This related to a tweet read out by presenter Pat Kenny during the final televised debate of the campaign, prior to which Mr Gallagher was regarded as the frontrunner.
A Twitter account with a user name similar to that of the official Martin McGuinness campaign, but not linked to Mr McGuinness, said a man who claimed he had given a €5,000 cheque to Mr Gallagher would appear at a press conference the next day.
Mr Gallagher has now claimed for the first time that the controversy cost him the election and apologised to the 500,000 people who voted for him.
"What happened in that studio on that night changed the outcome of the presidential election.
"On that evening, I let myself down and I let you the members of this council down and for that I’m truly sorry," he said at a meeting in Carrick-On-Shannon.
He said when Mr Kenny read out the fake tweet it "caused me to doubt my memory momentarily".
The Cavan man said he was aware of many people "who in that moment changed their mind and voted for another candidate".
"In that moment during the Frontline debate many viewers say me as somebody I am not. And that pains me greatly," he said.
Mr Gallagher, who is one of three Dragons’ Den investors in the race, said he fully accepts his own "failings" on the night.
"I should have stated that night that fundraising is a part of every political party.
"I regret not be more definitive and conclusion in my response to the specific accusation. There are very few of who don’t at some point wish we did things better.
"Mine was a very costly and publicly one," he said.
However, he concluded his 10-minute contribution by stating that he is back to fight a fresh battle.
"I am not seeking to be Michael D Higgins replacement. I am seeking to be successor and carry on the great work that he has done," he said.
Sir - Well done to Eilis O'Hanlon (Sunday Independent, August 26) for such a fair and balanced article in the midst of all the hysteria surrounding the Pope's visit to Ireland and to the Sunday Independent in general for providing balanced coverage of such a controversial event.
Imagine that Gavin Duffy's presidential campaign was a pitch on Dragons' Den. "So you're going to remortgage your house to raise a €750,000 loan to fund an enterprise with an almost zero chance of success? Er, I'm out."
Let's call it the week of 'Enter the Dragons'. Three panellists from a well-known television programme, 'Dragons' Den', pushed their case to become the nation's first citizen, chief overseas ambassador, and guardian of our law-making process.