David Letterman pulled no punches when asked about Donald Trump, whom he lambasted as a ‘damaged human being’ who may be in need of psychiatric help.

The 69-year-old retired talk show host also revealed that he was ‘proud’ that a segment from The Late Show showing him poking fun at Trump ended up in Hillary Clinton’s attack ad, and claimed that if he still had his bully pulpit, he ‘would have gone right after’ the GOP hopeful, unlike some of his successors in late night.

Letterman, who is currently promoting the New National Geographic series Years of Living Dangerously, shared his thoughts on the presidential campaign in general, and the Republican nominee in particular, in a candid interview with the New York Times Wednesday.

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Not too funny: David Letterman, pictured in May left, called Donald Trump, seen right at a campaign rally in Nevada on October 5, a 'damaged human being' who should be 'shunned'

'Perfect guest': During his 33 years as the host of The Late Show, Letterman would often invite Trump to appear on the show because he could take a joke and was, in his words, 'the perfect guest.' This screenshot is from Trump's appearance on the show in December 1987

Trump had been a frequent guest on The Late Show during David Letterman’s 33 years as the program's host.

Looking back on his past encounters with the real estate mogul-turned-politician, Mr Letterman said the quintessentially New Yorker 'big blowhard billionaire' was the 'perfect guest' who could take a joke at his expense and would roll with the punches.

When Trump came on the Late Show in 2012, Letterman produced some ties and shirts that were being sold under the Donald Trump brand at Macy's stores and pointed out that they were made in Asia.

That segment would later be prominently featured in a campaign ad for Hillary Clinton, accusing Trump, whose slogan is 'Make America Great Again,' of hypocrisy for outsourcing his merchandise overseas.

According to Letterman, Trump ceased being funny in his eyes the moment he began calling immigrants drug dealers and rapists after launching his presidential bid.

‘And everybody swallows hard,’ Letterman said. ‘And they think, oh, well, somebody will take him aside and say, “Don, don’t do that.” But it didn't happen.’

Badge of honor: Letterman said he was 'proud' and 'flattered' the Clinton campaign featured his on-air exchange with Trump in an attack ad

The ad seems to accuse Trump of being a hypocrite for making his line of clothing in Asia

Letterman also strongly condemned Trump for publicly mocking a disabled New York Times reporter while delivering a speech last November, saying that he believed at the time that it would be the end of his campaign.

‘Because if you can do that in a national forum, that says to me that you are a damaged human being,’ the veteran comedian explained. ‘If you can do that, and not apologize, you’re a person to be shunned.'

But that did not happen, and Trump went on to clinch the Republican nomination in July.

'The thing about Trumpy was, I think people just were amused enough about him to keep him afloat in the polls, because nobody wanted the circus to pull up and leave town,’ said Letterman of Trump’s success in the primaries.

When asked about his reaction to the Clinton TV spot showing his confrontation with Trump over his outsourced clothing line, Letterman said he was 'flattered' and 'pleased.'

Not impressed: Jimmy Fallon was criticized for failing to hold Trump's feet to the fire during an interview last month. Letterman says he 'would have gone right after him'

'I felt like I still have a small voice in this. I thought it was good,’ he told The Times.

Several late-night hosts, most recently Jimmy Fallon, have been roundly criticized for failing to hold Trump's feet to the fire when he would appear on their shows.

In response to a question about Fallon's lighthearted on-air exchange with Trump, Letterman said if he had a show, he 'would have gone right after him.’

'I would have said something like, "Hey, nice to see you. Now, let me ask you: what gives you the right to make fun of a human who is less fortunate, physically, than you are?” And maybe that’s where it would have ended,’ said Letterman.

He then added: ‘But if you see somebody who’s not behaving like any other human you’ve known, that means something. They need an appointment with a psychiatrist. They need a diagnosis and they need a prescription.’

This was not the first time that the outspoken TV veteran discussed Trump’s candidacy in unflattering terms.