Sienna Miller feels ''sad'' about the impact social media has had on fashion.

The 'Factory Girl' actress is a big fan of 1990s wardrobes as she thinks it was the ''chicest'' decade and much more ''original'' than style is now.

She said of the era: ''Women in oversized blazers and very little make-up.

''No one looked like they were trying too hard...

''I get sad looking back and seeing these pre-social media days, where people were wild and reckless, and nothing was contrived or over thought.

''There were these original moments in fashion - even though they didn't feel it at the time.''

Despite always being praised for her own sense of style, the 37-year-old actress - who has daughter Marlowe, seven, with former partner Tom Sturridge - doesn't always enjoy walking the red carpet and thinks the key to pulling off a look at a big event is to feel confident.

She told Grazia magazine: ''The red carpet itself is always a blur.

''I try to check out mentally and get through it. Often, a glass of wine before helps.

''I think you have to have a sense of self. A person who's wearing something as simple as black jeans and a T-shirt can radiate glamour, and that comes with self-confidence, being calm an centred.''

Living in New York has made Sienna give up high-heeled shoes.

She said: ''Flats for sure. I run around everywhere and New York is a walking town.''

Though the 'American Woman' actress shops ''a lot less'' these days, she still has her favourite haunts.

She said: ''I love Portobello Market and always have.

''It's so nostalgic for me and one of the first places I like to potter around when I get home.

''I seem to shop a lot less in New York but there is a great place called Personnel in the West VIllage that is beautifully curated. I always seem to find things there that I don't see anywhere else.''