Jay Leno has slammed Jimmy Kimmel for being ''mean''.

The former 'Tonight Show' host thinks the 'Jimmy Kimmel Live!' presenter is ''talented and funny'' but believes his show doesn't do as well as his rivals' in the ratings because he is lacking in kindness.

He said: ''The most [important] element you can have in doing a late-night show is kindness. Because the show makes you arrogant. I think that's Jimmy Kimmel's problem. I think he's a talented guy, I think he's funny. But he has a mean streak, and it comes across.

''He does this thing where he takes Halloween candy from kids and the kids cry. What am I missing here? It is funny I guess, but it's mean-based. I think that's why he's not higher in the ratings.''

The 65-year-old comic - who is a fan of his 'Tonight Show' successor Jimmy Fallon and 'Late Night' host Seth Meyers - is also backing Stephen Colbert to do well when he takes over as 'Late Show' host next month, following the departure of David Letterman.

He told TV Insider: ''I think Colbert will be good. He's a truly nice guy and decent human being.''

Jay thinks Jimmy Fallon is ''clever'' because he has rejigged the traditional format of the show after recognising the opening monologue is no longer viewed as important as it used to be.

He said: ''To me, the nature of the business has changed. The monologue doesn't have the weight it once had. It's different now.

''That's where Jimmy is clever. He does the viral videos and music things. That's what it's become. It's not better, it's not worse, it's just different.

''You only live in the time you live in. For our time, I would do a 12- to 14-minute monologue. But that has changed, and that's OK.''