Actor Simon Pegg certainly knows how to lose friends and alienate people.

The 38-year-old actor has launched an unprovoked attack on fellow comedian Ricky Gervais by saying that The Office star is an "idiot" and "fat".

The uncharacteristically scathing remarks came moments after Simon had been asked whether he - like Gervais - was feeling the pressure of the LA lifestyle.

Bizarre: Simon Pegg launched a verbal attack on fellow comedian Ricky Gervais

Instead of responding in his usually mild-mannered style, he said: "He says a lot of things, that man.

"He said there'd been no good British films since 1950. What an idiot."

He continued: "If you go to LA, you can get sucked into that.

"I've seen people go there and suddenly become rake thin because there is a slight pressure on you to be thin. I've also seen a lot of fat people there."

When the topic of Gervais's portly figure was later brought up, Simon rubbed salt into the wounds by adding: "He's one of the fat people in LA, yes."

Unlike most public feuds between celebrities, Simon's outburst - aired on the Jamie Theakston and Harriet Scott show on Heart FM - does not follow a personal attack from Gervais.

An insider told us: "It was one of the most bizarre moments of the show.

"It was completely unexpected by [Simon], as he usually never says a bad word about anyone.

"At one stage both Jamie and Harriet laughed because they didn't know how to take his comments. He was being serious."

Simon was on the red carpet in Leicester Square last week for the premiere of his new movie How To Lose Friends And Alienate People.

It's based on writer Toby Young's memoir documenting his time working for Vanity Fair magazine in New York.

Simon was at the premiere with heavily pregnant co-star Gillian Anderson, who joked: " I ' m so close to popping out."