CNN host Don Lemon calls women in their 50s past their 'prime'

US news anchor Don Lemon startled colleagues and enraged viewers when he suggested on CNN's morning show that Republican presidential candidate Nikki Haley, at age 51, was past her prime.

Lemon, along with CNN This Morning co-hosts Poppy Harlow and Kaitlan Collins, was discussing Ms Haley's suggestion a day earlier that politicians over age 75 should be subject to mandatory mental competency tests.

President Joe Biden is 80 while another Republican presidential candidate, former president Donald Trump, is 76.

“Nikki Haley isn't in her prime, sorry,” Lemon said, explaining why he was “uncomfortable” with the age discussion. “When a woman is considered to be in her prime — in her 20s, 30s and maybe her 40s.”

“Prime for what?” Harlow replied.

Lemon said that if you look it up on Google, a woman is considered to be in her prime at those ages.

Harlow tried to clarify what Lemon was referencing: “I think we need to qualify. Are you talking about prime for childbearing or are you talking about prime for being president?”

“Don't shoot the messenger, I'm just saying what the facts are,” Lemon replied. “Google it.”

Ms Haley tweeted out a video of the CNN exchange on Thursday, saying: “Liberals can't stand the idea of having competency tests for older politicians to make sure they can do the job. BTW, it's always the liberals who are the most sexist.”

He brought up the subject again an hour later, when commentator Audie Cornish joined the discussion.

Like Harlow had earlier, Cornish said the idea of “prime” that Lemon was referring to was about reproductive years, and did not concern mental health and ageing.

“She's in her prime for running for office,” Cornish said of Haley, who announced her candidacy Tuesday. “Political prime is what we're talking about.”

Later on Thursday, Lemon issued a statement saying he regretted his “inartful and irrelevant” references to a woman's prime age.

“A woman's age doesn't define her either personally or professionally,” he wrote on Twitter. “I have countless women in my life who prove that every day.”

There was no immediate comment from CNN leaders.

CNN chief executive Chris Licht launched the network's new morning show in November.

The Associated Press contributed to this report