Fianna Fáil leader Micheál Martin has described Donald Trump's remarks about four US congresswomen as "racist".
Mr Trump's call for four Democratic congresswomen to "go back" to their ancestral countries has sparked huge controversy and drawn widespread condemnation in recent days.
Taoiseach Leo Varadkar was accused of a 'fudge' after he said the remarks had the "hallmarks of racism" but insisted he wasn't calling Mr Trump a racist.
Mr Martin initially described Mr Trump's comments as "outrageous" and "ridiculous" - but stopped short of labelling them as racist - while speaking to journalists earlier this week.
However, responding to a query from the Irish Independent yesterday, he said: "I believe President Trump's comments were totally unacceptable, un-American and I believe them to be racist."
Mr Martin signalled that he would still be prepared to visit the White House and meet with Mr Trump despite the racism storm engulfing the president, who has denied he is a racist. He was further criticised following a rally on Wednesday when the crowd shouted "send her back" after he referenced Democratic congresswoman Ilhan Omar, who is Somali-born.
"I take great exception to what he said. I think it was outrageous and totally at variance with the spirit at the core of the American nation which is about all races and all creeds coming together. I mean that was the origins of the American state," he said.
Mr Martin said the comments were indicative of a "more sharply divided, polarised" US political environment. Asked if he would stand up to Mr Trump if he was Taoiseach, Mr Martin said: "I would stand up for the values that I believe in as a democrat and a parliamentarian."