Sienna Miller wants to become a couture designer.

The actress-turned-designer and her sister Savannah stepped down as co-creative directors of their fashion label Twenty8Twelve in 2012, but Sienna insists she wants to continue working in fashion.

In the new edition of Nylon magazine, she said: ''We were designing a really big collection in the end ... I think maybe I'd be more fulfilled being a couturier or something, or doing 10 amazing pieces a season.''

The sisters decided to separate themselves from the label, which was launched in 2007, in order to pursue other ventures and it continued under the current design team and was renamed Twenty8Twelve London, instead of Twenty8Twelve by s. miller.

Managing director Nish Soneji said at the time: ''We've had a great partnership with the Miller sisters.

''From the beginning, our mission was to create a contemporary label with its own identity and strong directional design, as well as an emphasis on quality, cut and finishing.''

Twenty8Twelve has three stand-alone retail boutiques in London and their designs are sold in over 300 carefully selected retailers.

Meanwhile, Sienna, 32, has been focusing on bringing up her 20-month-old daughter Marlowe with fiance Tom Sturridge and said after ''crazy'' times during her 20s, motherhood has changed her outlook on life.

She said: ''Nowadays, I can be the woman I truly am, more calm, and freer too. I turned 30 and I suddenly had much less energy!''