US President Donald Trump's assertion that he had heard Ireland was going to cut its already low corporate tax rate is "fake news", Irish Prime Minister Leo Varadkar said on Wednesday.

Trump raised a few eyebrows in Ireland on Monday when he told reporters at the White House: "I hear that Ireland is going to be reducing their corporate rates down to 8 per cent from 12."

"I can confirm that President Trump's claim that we are proposing to reduce our corporation profit tax to 8 per cent is indeed fake news. There is no such plan to do so," Varadkar told parliament in answer to a question on Trump's comments.

Ireland's 12.5 per cent corporate tax rate has long made it a hub for investment from major US multinationals like Google and Facebook and a target for criticism from US politicians.