Former senior Ulster Unionist Lord Kilclooney has been criticised for calling Irish prime minister Leo Varadkar a “typical Indian”.
He tweeted the comment in response to a news story in which Mr Varadkar was accused of “poor manners” over his visit to Northern Ireland on Monday.
Former Ulster Unionist leader Mike Nesbitt tweeted that he could only interpret it as a “racist comment”.
Lord Kilclooney told BBC News NI he rejected “false accusations of racism”.
He also said that he did not intend to withdraw the tweet.
It is the second time the peer has been criticised over a tweet about Mr Varadkar.
Last November, a tweet in which Lord Kilclooney referred to the Irish prime minister as “the Indian” was described as racist.
He later withdrew the tweet. A complaint to the House of Lords standards commissioner was dismissed.
Of his latest tweet, Lord Kilclooney told the BBC that Mr Varadkar had been “most provocative” over the course of the Brexit negotiations and had “misunderstood the views of many unionists”.
He added that Mr Varadkar had a “dismal lack of knowledge” about Northern Ireland affairs.
Lord Kilclooney also tweeted that “it is not racially abusive as he himself has confirmed he is half Indian” but that Mr Varadkar “has damaged North/South relations by being continually offensive and provocative to the Unionist majority in NIreland”.
Alliance Party leader Naomi Long said Lord Kilclooney was “an embarrassment”.
She told the BBC that the comment was a “slur on all Indian people with his use of the word typical”.
She added that she wants the speaker of the House of Lords to raise the matter with Lord Kilclooney.
Irish senator Niall O Donnghaile, of Sinn Fein, said he would ask the speaker of the Irish senate to contact the speaker of the House of Lords “urging him to take appropriate action regarding yet another offensive tweet from a member of the House of Lords regarding An Taoiseach Leo Varadkar”.
Democratic Unionist Party (DUP) MLA Christopher Stalford tweeted: “I don’t know what John Taylor (Lord Kilclooney) thinks he’s playing at but he doesn’t speak for me. Absolutely ridiculous behaviour.”
Mr Varadkar was born in the Republic. His father is Indian and his mother is Irish.
He was elected taoiseach (Irish prime minster) in June 2017.