Victoria Beckham says her Posh Spice persona stemmed from insecurity.

The former Spice Girls star admits she has always looked ''moody'' but insists she is just ''shy'' and can't help but reverting back to the character she created when out in public.

She said: ''I looked moody. But I wasn't! I was shy, not very sure of myself.

''I had to invent a character and I thought of that: staring at people and pouting. My insecurities helped me create the character in a way. Nowadays, it's like a barrier that comes back whenever I go out in public. That's the way fame has affected me.''

The 39-year-old fashion designer - who has children Brooklyn, 14, Romeo, 11, Cruz, eight, and Harper, two, with husband David - insists her fame doesn't stop her carrying out everyday tasks, even if doing the weekly food shopping for her family attracts a lot of attention.

Speaking to VOGUE Paris magazine, she said: ''It's always me who goes to Waitrose to do the weekly shop, Harper balancing on one hip, Brooklyn hanging onto the trolley. I go down the aisles telling the kids, 'No, you can't have that!', just like any other mother. People look at me in awe like I'm from the circus, but it doesn't bother me.''

The Spice Girls reformed in 2007 after seven years apart and Victoria admits she had lost her ''passion'' for the group, who also got together for a one-off performance at the 2012 London Olympics closing ceremony.

She explained: ''I realised it was finished for good in 2008, when we reformed for our reunion tour.

''It should have been the best moment of my life, but I just wanted to be elsewhere. It wasn't a lack of respect for the girls or the audience, but the passion just wasn't there. By contrast, in my new career, the passion grows every year. I still want more.''