Taoiseach Enda Kenny has said he was paying tribute to Barack Obama by using elements of the US president's famous victory speech in his College Green address.
Mr Kenny's rousing speech sparked applause and cheers from the crowd but the opening section drew striking similarities to Mr Obama's 2008 speech at Grant Park in Chicago.
Mr Kenny said the first 40 words of his 470-word address introducing the president was from the victory address.
"It was a tribute to the president of the United States as distinct from anything else," the Taoiseach said. "That's one of his most famous speeches and it hangs in my office."
Earlier a government spokeswoman denied he was plagiarising Mr Obama and said Mr Kenny merely echoed the sentiments expressed in the now world-famous speech to make it relevant for an Irish audience.
"I think what the Taoiseach was doing was drawing on a very well-known speech by Barack Obama and just putting it into an Irish context and an Irish setting," she said. "There was no plagiarism, he was just drawing on it."
Mr Kenny's address was peppered by spontaneous applause from an emotional crowd when he talked of how the president had come home and the strong ties between the two countries.
President Obama and his wife Michelle warmly applauded the seven-minute speech, which included the same inspirational introduction that President Obama himself used to woo fans on the momentous November night three years ago.
Mr Kenny said: "If there's anyone out there who still doubts that Ireland is a place where all things are possible; who still wonders if the dream of our ancestors is alive in our time; who still questions our capacity to restore ourselves, to reinvent ourselves and to prosper, well today is your answer."
Mr Obama in 2008 said: "If there is anyone out there who still doubts that America is a place where all things are possible; who still wonders if the dream of our founders is alive in our time; who still questions the power of our democracy, tonight is your answer."