David Letterman: 'I stayed on network TV for too long'

David Letterman hosts his final broadcast of the Late Show with David Letterman, Wednesday May 20, 2015 on the CBS Television Network. After 33 years in late night television. Photo / Getty

David Letterman thinks he should have retired from 'The Late Show' a decade before he did.

The 71-year-old broadcaster stepped away from the programme in 2015 after more than 30 years and while he believes he outstayed his welcome, he claimed no one had "the guts" to fire him.

Speaking on The Ellen DeGeneres Show, he said: "Yes it is true, and I'll tell you what happened.

David Letterman in conversation with senator Al Franken at 92nd Street Y on May 30, 2017 in New York City. Photo / Getty

"It turns out nobody had the guts to fire me. And I should have left like 10 years ago. You want to make sure you have some energy to direct toward other things."

David praised the 'Finding Dory' star for doing other things alongside her long-running show and admitted he should have done more himself.

He said: "I did not. All I cared about was myself. I was looking through the wrong end of the telescope."

Elsewhere on the programme, the presenter - who now hosts 'My Next Guest Needs No Introduction' on Netflix - recalled a funny incident in a hotel that left him convinced he was going to be sent to prison.

Ellen's producer Mary used to work on The Late Show and she and David were once playing catch on the 14th floor of 30 Rockefeller Plaza in New York City - only to accidentally break a window with a baseball, which flew down onto the crowds outside.

David quipped: "Well how many are dead?

"So I'm stunned and I go over to where the window is and I'm just kind of hiding and looking down there...and people were looking up because shards of glass had rain down on the Avenue of America. And I see a guy down there point up and go, 'Oh hey there's David Letterman!' and I just thought I was spending the rest of my life in prison."