In a statement to CNBC, Kudlow said he was "disappointed and saddened" to learn of Brimelow's views. "If I had known any of that I never would have invited him. I don't agree with any of that."
Kudlow was a longtime contributor at CNBC before joining the Trump administration. His birthday party came one day after White House speechwriter Darren Beattie was dismissed in the wake of reports that he had spoken alongside Brimelow at a panel in 2016.
Kudlow's public views on immigration stand in contrast to Brimelow's. In a 2014 column for CNBC, Kudlow wrote that he supported immigration as a "pro-growth" issue and advocated outreach to "Latinos, African-Americans, young people and women."
A White House representative did not immediately respond to a request for comment.