FACTORY GIRL star Sienna Miller was mortified during an interview with US talk show host DAVID LETTERMAN when he played an embarrassing clip of her cursing on live TV.

Miller appeared on US breakfast show TODAY last month (31JAN07) and was filming a live promotional spot for her upcoming segment when she let a profanity slip as the show cut to commercial.

The ALFIE star was appalled when she learned her slip-up caused such a stir saying, "I heard about it. I just got informed. I'm horrified. I had no idea.

"It's that thing where you're sitting there and you feel like a complete lemon. It's not three seconds, it's ten of you just sitting there (smiling) and you don't know what to do!

"I heard that I swore...which does sound like me, I have to admit."

Letterman then re-played the segment as Miller covered her face in embarrassment.

The talk show host later joked about the incident when he asked Miller what clip was going to shown from her film Factory Girl.

When she hesitated, Letterman quipped, "Oh, what the f**k do you care," which elicited huge cheers from the crowd.

A shocked and delighted Miller said, "David Letterman! Well done! That's brilliant! I cannot believe you just said the f-word!"