Lord Kilclooney has claimed that five complaints made to the Westminster standards commissioner about a tweet in which he described the Taoiseach as a "typical Indian" are unrepresentative of the people of Northern Ireland.
The peer later withdrew the tweet about Leo Varadkar but denied he was racist. Complaints have been made to the commissioner for standards at the House of Lords, Lucy Scott-Moncrieff.
Lord Kilclooney said he had deleted his tweet when it became clear the claim on which it was based - that the Taoiseach had breached protocol on a visit to Northern Ireland - was wrong.
"Of the five who complained at least two are nationalist politicians," he said.
"More than 1.8 million people in Northern Ireland did not complain and knew the tweet was deleted."
Ms Scott-Moncrief has begun an initial investigation into the tweet and will consider if Lord Kilclooney has breached any rules.
SDLP MLA John Dallat is among those who have complained. An SDLP activist in south Belfast, Seamas de Faoite, has also lodged a complaint.
Mr de Faoite claims the peer's comments breach the code of conduct for peers and are "discriminatory and prejudicial against anyone from, or with heritage connected to, the nation of India".
In a letter to the commissioner, he claimed Lord Kilclooney "has fallen short of the standards expected of a public representative, specifically the seven general principles of conduct identified by the Committee on Standards in Public Life".
The SDLP man also said the tweet had caused "hurt and insult to the people of Ireland who are represented by An Taoiseach and his government".
If Lord Kilclooney is found to have breached the code of conduct, the report will be presented to a sub-committee, which will recommend a course of action.
Peers can be expelled if judged to have breached the code of conduct.