Los Angeles, Aug 22 (IANS): Actor Gerard Butler accidentally flashed 400 guests at his sister's wedding as he forgot he was not wearing an underwear underneath his kilt.

"The Ugly Truth" actor wore a traditional Scottish kilt, which is worn without an underwear, to his sister Lynn's wedding. He said that after forgetting to keep his legs together when he sat down, he ended up accidentally flashing all 400 people who attended the ceremony, reports femalefirst.com.

Speaking on the talk show "Conan", he said that he has not worn kilts much.

"We're born in kilts. They are the worst diapers... I've not worn a kilt as much as you'd think. I wore a kilt at my brother's wedding and at my sister's wedding, and I loved it both times, but they were both disasters.

"At my sister's wedding I had to do the first reading, it was a Catholic wedding, there's, like, 400 people in the congregation. So I'm sitting, and my mum's in the front row and she's looking up at me, and I'm looking down at her. And my mum ... she does this pious like (puts his hands together) and I think she's telling me to pray.

"I think she's saying 'Please pray, you should be doing this'."

The actor said he sat and put his hands together.

"And she goes 'No no no'. I look down, and my kilt is spread wide, facing the whole congregation. So I slowly like... crossed my legs. We don't wear underwear under a kilt, you're not supposed to. I, definitely, that day, was not wearing an underwear."