Christina Aguilera is rarely seen without her signature red lipstick and heavy eye make-up, calling it her ‘armour’.

So it must be quite a challenge for the singer to part from her beloved war paint as she goes for the natural look in her upcoming film debut.

Spotted on the set of Burlesque in Los Angeles yesterday, Aguilera, 29, looked unrecognisable with her golden blonde wig and natural make-up.

Who’s that girl? Christina Aguilera looked unrecognisable with her golden blonde wig and natural make-up

Made up: Aguilera with bright red lipstick and smoky eyes on New Year’s Eve in Las Vegas

The film sees Aguilera play a small-town girl called Ali who flees home for a new life in Los Angeles.

After landing a job as a cocktail waitress in a burlesque club, she soon aspires to become one of the sexy dancers on stage.

Aguilera has always spoken openly about her love of cosmetics, believing its her responsibility as an entertainer to look immaculate at all times.

She said: ‘The red lips are – I don’t want to call them “armour,” but they’re the clothes of my character, and I’m in the business of entertainment.

‘I don’t see make-up as a defence. I see it as a creative outlet.

‘Who’s to say a little mascara doesn’t make you feel more confident when you pop it on and look in the mirror?

‘It helps, especially in my position, where I have people waiting down the street to take pictures of me so they can evaluate and criticise every little flaw on my face. I suppose that’s where the armour would come into the picture.’

Small town girl: Aguilera transformed from glam pop star to aspiring burlesque dancer in the new film

Despite her love for red lipstick, Aguilera recently admitted she was forced to change from her favourite brand to find a more kiss-proof laquer.

She said: ‘I love having red lips. There’s just something fun and vibrant about it. I love that extra little “pop” to any look no matter how simple or strong the rest of the face is.

‘But I have been using this kiss-proof red lipstick recently so I can kiss (my son) Max without getting kiss marks all over him.’

As well as losing the heavy make-up for the role, Aguilera has also been shedding the pounds.

The star has been looking noticeably less curvier in recent months due to her daily dance routine.

Slimmed down: Aguilera has shifted the pounds with a combination of dance and weight lifting

She is spending up to 14 hours a day rehearsing for the film, which is due for release later this year.

Her trainer Tee Sorge says Aguilera has been hitting the gym in addition to practising in the dance studio.

Sorge said Aguilera has been lifting weights and doing between 300 to 500 sit-ups a gym session.

Sorge told InTouch magazine: ‘She’s tremendously happy and feels really strong. We want to make sure she doesn’t lose her muscle mass or too much weight.

Caffeine fix: Aguilera sips a cup of coffee in-between scenes

‘We work the entire upper body by doing everything from bicep curls to tricep dips. Christina does three sets of each exercise and uses weights ranging from five to 15 pounds.’

Aguilera has also banished all whites from her diet, including flour, rice and sugar, but is allowed one day off a week to eat what she likes.

Sorge added: ‘She’s always been good. But now she’s sticking to whole grains and lean proteins. Her goal now is just to be fit.’