Sienna is also excited about the range, called Twenty8Twelve, that will launch in September. The line has been named after the actress’ birthday.

"Sav has been the closest person to me my whole life," Sienna smiled. "Now I’m working with her - what could be more fun?"

She previously said she plans to be very hands-on with the project.

"This isn’t about just lending a name to something and not really being involved," she said.

Savannah is a graduate of Central Saint Martins and has also previously lent her talents to Alexander McQueen, Betty Jackson and Matthew Williamson.

Sienna backs worldwide shape-up - June 4 2007
If Sienna Miller’s new workout catches on, it could help save more than our waistlines - the entire planet, in fact.

She’s backing a new programme that helps you shed a different kind of pound, the carbon kind.

"My CO2" is billed as a way for individuals to "shed tonnes" by reducing their carbon emissions.

An online guru called the Carbon Coach takes you through simple lifestyle changes that can reduce your carbon footprint.

Joining Sienna in the battle for environmental fitness, set up by charity Global Cool, are Josh Hartnett and Heather Graham.

Heather, who has committed herself to saving 1.5 tonnes of carbon through the new ’diet’, said: "Think of it as a new workout, a simple, straightforward workout to save the planet."

Sienna annoys neighbours - May 25 2007
Sienna Miller’s neighbours have apparently spoken out about the blonde actress’ late night parties.

The Factory Girl star is well known for her love of partying - but it seems her neighbours aren’t quite so keen and the nearby residents of Sienna’s pad in Marylebone, North-West London, say the noise during the early hours is unacceptable.

One told the Independent: "She has parties with bouncers outside that sometimes last until daylight.

"The music’s so loud it rattles our windows. When someone’s gone round to complain, the music’s turned down a bit then turned up when they’ve gone. We’re going to call the noise police if it carries on."

The curtain-twitching neighbour also added that it has been more peaceful in the area for the past three weeks - because Sienna has been filming the Dylan Thomas biopic, the Edge Of Love, alongside Keira Knightley and Matthew Rhys, in Wales.

The neighbour moaned: "I am dreading her coming back because the music will start again."

A spokesperson for the actress said they did not comment on her private life.

Sienna does Hippie Hippie Shake - May 4 2007
Sienna Miller is to star alongside Cillian Murphy in a film about 1960s London, according to reports.

The pair will star in Hippie Hippie Shake, about Australian magazine editor Richard Neville who became embroiled a landmark obscenity trial after publishing a sexually explicit edition of Oz magazine.

The Hollywood Reporter says Cillian, 27, will take on the role of Neville, with Sienna playing his partner Louise Ferrier.

The screenplay has been written by Lee Hall, who wrote Billy Elliot, and will be directed by Bridget Jones: The Edge Of Reason’s Beeban Kidron. Shooting is expected to being in London this autumn.

Sienna is currently working with Cillian on Dylan Thomas biopic The Best Year Of Our Lives. The 25-year-old is no stranger to playing 1960s sirens, having starred as Edie Sedgwick in Factory Girl.