Former South Carolina Gov. Nikki Haley has responded to "sexist" remarks made by CNN host Don Lemon, who said Thursday that the Republican presidential candidate was not in her "prime" and that discussions about age and competency for politicians made him "uncomfortable." 

"Liberals can't stand the idea of having competency tests for older politicians to make sure they can do the job," tweeted Haley, 51, who announced this week that she will seek the GOP nomination for president in 2024.

"BTW it's always the liberals who are the most sexist," she added.

CNN'S DON LEMON AWKWARDLY CLAIMS NIKKI HALEY 'ISN'T IN HER PRIME' AS CO-HOST BALKS

Lemon, who commented on Haley's age Thursday on "CNN This Morning," quickly faced criticism for his comments, even from his co-hosts.

"This whole talk about age makes me uncomfortable. I think it’s the wrong road to go down. She says people, you know, politicians are something if not in their prime. Nikki Haley isn't in her prime, sorry. A woman is considered to be in their prime in 20s and 30s and maybe 40s," said Lemon, who is 56.

Co-host Poppy Harlow questioned what he meant by "prime" and Lemon said that it wasn't according to him.

NIKKI HALEY CALLS FOR POLITICIANS OVER 75 TO FACE 'MENTAL COMPETENCY TESTS'

Nikki Haley

Nikki Haley, former ambassador to the United Nations, formally announced her run for president in 2024 during an event in Charleston, South Carolina, on Wednesday. (Sam Wolfe/Bloomberg via Getty Images)

"It depends, just like 'prime,' if you look it up. If you Google it, when is a woman in her prime, it'll say 20s, 30s and 40s," Lemon responded. "I’m not saying I agree with that. I think she has to be careful about saying that, you know, politicians are in their prime."

Harlow followed up again and asked if Lemon was talking about "prime for child bearing" or "prime for being president."

"I’m just saying what the facts are. Google it. Everybody at home, when is woman in her prime, it says 20s, 30s and 40s. And I’m just saying should be careful about saying that politicians are not in their prime and they need to be in prime when they serve. Because she wouldn't be in her prime…," Lemon said.

Lemon's comments came as the hosts of the program discussed President Biden's age ahead of the 2024 presidential election, as well as Haley, who called Wednesday for a rule requiring politicians over 75 to take "mental competency tests" in an effort to evaluate their ability to serve in office.

Don Lemon, Nikki Haley

CNN host Don Lemon said Thursday that Nikki Haley was not in her "prime" and that discussions about age and competency for politicians made him "uncomfortable." (Theo Wargo | Dimitrios Kambouris)

CLICK HERE TO GET THE FOX NEWS APP

"In the America I see, the permanent politician will finally retire," Haley said as she formally announced her run for president from Charleston, South Carolina. "We’ll have term limits for Congress and mandatory mental competency tests for politicians over 75 years old."

Haley's proposed rule would impact former President Donald Trump, 76, who has declared his candidacy for president in 2024, and President Biden, 80, who has not yet made his plans official.

Fox News' Hannah Panreck and Anders Hagstrom contributed to this article.