Gwyneth Paltrow says Stella Mccartney is ''a bit naughty''.

The 40-year-old actress described the fashion designer as her ''sister'' in an emotional post in her lifestyle newsletter Goop in which she also claimed the pair share ''similar values''.

She wrote: ''Sometimes in life you get a girlfriend who becomes like a sister. Someone who really sees you. Who is as honest with you as they are loving. Who shares a similar world view, who has similar values.

''Who is a bit of a life raft when you live in a country that you lovingly adopt, but is not your own. Who also happens to be hilarious and a bit naughty and is constantly trying to get the balance of everything right, just like you are.

''Who is also one of your favorite designers ever, who has a ruthless eye and makes perfect, perfect things. Stella is that girl and so much more.''

In the post, Gwyneth also revealed they had paired up on a ''very mini'' collection which featured black and navy jeans and a black wool blaze, among other items.

She continued: ''I convinced her to do a collaboration, a very mini capsule collection of some beautiful, covetable things.''