Dara Calleary says he had an "incredibly difficult" conversation with Micheal Martin and was "angry" when he was not appointed to a ministerial role.
The Mayo TD was a shock omission from the ministerial ranks of Michéal Martin's government on Saturday, though he will sit at cabinet as Chief Whip and junior minister at the Department of the Taoiseach.
"It wasn't the weekend I expected," Mr Calleary said.
"But I'm absolutely blown away by the hundreds of people who have been in contact since Saturday.
"I understand from media reports, I was the last person brought into the room, I'm not going to go into the private and incredibly difficult conversation.
"What he said to me was that the Chief Whip's role is going to be incredibly difficult in a three-party government, and he identified me as the person with the skill to do that to work, to implement the programme for government and is confident that I would be able to do that.
"It was a lengthy discussion and he was particularly focussed on me taking this job, there were no other jobs on the table offered to me, and wasn't given the opportunity to think about it.
"We had a difficult conversation, I told him I was disappointed, I had hoped to lead a department, and still is my ambition today, it will happen.
"It's been a difficult time, but it's what you do with that difficulty.
"I have an opportunity now to repay that to the country in this term of government."
Mr Calleary said he was "proud to be a member of Fianna Fáil", and had "worked incredibly hard in the 13 years" he has represented Mayo.
Mr Calleary has been one of the most prominent Fianna Fáil politicians in the last number of years and was widely expected to receive a high-level ministry after impressive work during government formation negotiations.
Local outrage has not subsided since the apparent snub and many Mayo residents wrote into MidWest radio ahead of Mr Calleary's appearance on the programme. Many said the appointment was "absolutely disgusting", and "an insult to Mayo people", which shows Micheal Martin is "desperate for power".
Mr Calleary said the comments were "strong words" that "reflect the anger I got from messages".
"I get where that's coming from, but I'll be around the table and I will be a strong loud and constructive voice, working with other ministers, they're not going to forget the west exists and the challenges we face," he added.
"As chief whip I will be in their ear on a daily basis on government business and the west, ensuring that they deliver on promises in the programme for government, which has a huge amount of ambition for regions and I wrote those into it and I will make sure they're delivered.
"I hear the anger and will take it on and turn it into action and let it drive me on around cabinet table.
"I've had lots of contact and advice from people who formerly held the office today.
"I was that angry person yesterday but I'll dust down and make the most of it, and I'm really grateful and blown away by the response I got from people, I'll return their faith in me in spades."
Chairman of Ballina Comhairle Ceantair Matt Farrell has said that there would be "no welcome to Micheal Martin from any of the Fianna Fail people in the area, and it will be a long time before he'll show his nose in Ballina or Mayo again".
When pressed on the issue, Micheál Martin said the chief whip was "an important position" and "quite a number of the party" were upset about being left out of cabinet.
"It's very difficult and I have no doubt people will be disappointed," he said.
"It's done on a range of criteria, and every time a cabinet is appointed there is disappointed."