The Fianna Fáil leader claims Donald Trump's 'racist' comments are 'outrageous'.
The US president suggested four Democratic congresswomen should go back to the 'crime-invested' countries they come from.
The House of Representatives condemned his comments - but Trump denied they were racist.
Micheál Martin is the latest political leader to criticise his remarks saying he takes great exception to President Trump's comments.
He believes they are at variance the standards that are at the core of the American nation.
Micheál Martin also says the remarks were 'ridiculous'.
One of the women, Democrat congresswoman Ilhan Omar, also became the target of racist chants at a presidential rally this week. But at Minneapolis-St Paul International Airport, her supporters had a counter call - shouting "welcome home, Ilhan" with wide smiles.
Mr Trump has cast his fight with Ms Omar as a battle of ideas - another episode in an us versus them presidency.
The president and some of his supporters view Ms Omar as anti-Israel and anti-American, and the senior Republican leadership have backed him.
The so-called Squad she is part of say they want to avoid taking the bait and playing into Mr Trump's hands.