Reese Witherspoon feared she would wet herself on set while working with Vince Vaughn.

Dismissing rumours there was friction between her and her comic co-star on new movie ‘Four Christmases’, the actress claims it was the most fun she’s ever had making a movie.

She said: “Vince is the funniest person I've ever worked with in my entire life.

“There were days when we were shooting things, I would laugh so hard it would ruin the take, and I was afraid I was going to pee myself, it was so funny.”

Witherspoon — who has two children, nine-year-old Ava and four-year-old Deacon, with ex-husband Ryan Phillippe — also revealed she is “very happy” with boyfriend Jake Gyllenhaal.

The Oscar-winning actress admits it is a great comfort to be in a relationship with such a loyal partner.

Witherspoon (32), added to America’s Vogue magazine: “Jake is very supportive.

“Suffice to say, I'm very happy in life and I'm very lucky to have a lot of really supportive people around me who care very much for me. You know, that's all you can hope for in life. I am very blessed in that way.”