Green Party leader Eamon Ryan says he "deeply" regrets falling asleep in the Dail last week and conceded it could damage him in his battle to stay at the party's helm.
Mr Ryan said he "nodded off briefly" during voting on a Social Democrats motion on workers' rights last Thursday.
He said that he did actually vote and that he believes he was one of the few party leaders there, but added: "I regret it deeply."
Mr Ryan told RTE Radio's This Week programme "it was a moment of human frailty".
"You have to make sure that you continue and actually make sure you learn from such mistakes and stay alert every time, and I will be doing that," he added.
Mr Ryan rejected criticisms that have been made in recent days that he had to be woken up to vote against a motion designed to protect workers.
He said there was "no excuse" for falling asleep but insisted: "We were not denying workers' rights."
The Transport Minister said he voted in support of a government amendment which commits to protecting workers.
He said that his job is to attend Cabinet and help develop an economic stimulus - due to be announced tomorrow - which "lifts this country and helps those workers out of difficulty".
"My job is to deliver jobs for the people in our country to help us out with a difficult period and I think I have the ability to do that," he said.
"I've been giving my everything, working night and day all the time, flat out, full steam.
"It's through that work I hope I can serve those people."
He conceded that the incident "may well" harm him in the leadership battle against Catherine Martin with Green Party members voting this week.
Mr Ryan said he would remind members that "under my leadership it has been the most successful period in the history of the party".
He said he wants to use his experience to lead the party through the "difficult" period ahead.
"It's going to be a very hard period because the country is in a difficult crisis - the whole world is - but I think I have the skills to actually do that well.
"I'm committing to doing everything I can to deliver on it and I hope they will vote for me on that basis," Mr Ryan added.