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Sienna Miller has been told by lover Rhys Ifans, "Marry me or it's over". The Notting Hill actor issued Sienna with the ultimatum during their recent romantic trip to New York.

A source said: "Rhys is fed up with all the secrecy around their relationship and wants to make it a permanent thing.

"He has asked Sienna to marry him and it's the last time he will ask. He wants everyone to know they are officially an item."

Rhys has told Sienna they must announce their engagement now or end the relationship, but the Edge of Love actress is refusing to be pushed into making a commitment.

The source is quoted on the Daily Mail website as saying: "Sienna has yet to make a decision and Rhys can't understand why. Sienna is always trying to avoid the official relationship topic and is happy to keep it a low-profile affair. Rhys has been happy with that but now feels they should decide whether it's going to be long-term or not."

In December, Rhys bought Sienna an engagement ring for her 26th birthday, and hid the specially designed band among a pile of presents.

Rhys - who was first romantically linked to Sienna in August after he moved in to her London home when his houseboat started leaking - has reportedly asked the blonde star to marry him several times.

Last November, he is believed to have proposed to the actress by serenading her with a poem entitled 'Marry This Misfit'.

British actress Sienna Miller admits she enjoyed stripping for the movie "Hippie Hippie Shake", although she was embarrassed after her pictures appeared online.

Miller also said it wasn't as traumatic as she thought it would be.

"There were eight of us and we were playing hippies and it was the summer of love.

We take our clothes off, eight boys and girls, and go for a swim. We were nervous but it's real camaraderie when you're all together.

It's actually hilarious getting naked in front of people you love and respect," dailysnack.com quoted Miller as saying.

The movie is a psychedelic journey through London in the sixties and early seventies focusing on the love between the character played by Miller and the one played by actor Cillian Murphy.

She added: "The water was freezing cold, so the boys weren't too happy. The water was about seven degrees, it was colder than anything I've experienced in my life.

But as a result it was quite funny and we felt a big sense of achievement after doing it."

Sienna Miller has been stripping off to play a hippie - complete with flowers in her hair - in an upcoming role.

The 25-year-old is known for her bohemian fashion sense and it seems that now she is taking that sensibility one step further.

In her role in movie Hippie Hippie Shake, Sienna plays artist Louise Ferrier, the girlfriend of Australian underground magazine editor Richard Neville. Margo Stilley and Cillian Murphy also have parts in the swinging 60s film.

The actress is no stranger to the era, having taken on the role of Andy Warhol's muse Edie Sedgwick in biopic Factory Girl.

According to the Daily Mail, directors of Hippie Hippie Shake have asked Sienna to change her exercise routine so that she can develop a more rounded figure for the role, as well as dying her hair from blonde to brunette.

One insider claims Sienna is 'perfect' for the part: "She is not shy when it comes to stripping off and it is little wonder."

"She has always been praised for her distinctive boho look and even without clothes, she pulls this off."

Sienna is currently still filming the flick in various UK locations. Hippie Hippie Shake has a release date of sometime in 2008, but we'll let you know when they make it official.

Sienna Miller and Keira Knightley lashed out at the London paparazzi during their recent night out in the city.

The British beauties, who have been spending a lot of time off-set with each other after working together in a new movie, gave an abusive lecture to the shutterbugs on how to treat starlets.

"We're not on the f**king red carpet, we're on the street!" TMZ quoted Sienna, as telling the snappers.

After completing a week's work on their forthcoming Dylan Thomas movie, "An Edge of Love," the duo demanded to be left alone.

Sienna offered the paparazzi a deal, a few shots in return for some time alone.

"You never f**king get it cause you're all c**ts and make our lives hell ... we'll walk down the street, but we're not going to stand here and pose ... if you get a photo that's fine but then its a deal that you go!" Miller said.

Keira also supported her new found best pal, requesting the paparazzi to let them have a “nice night.”

"It would be really great if you let us have a night off ... we're just trying to have a nice night,” Keira said.

The pair hit the town last week in matching black boots, tights and sporting similar short dresses.

Accompanying them was Keira’s boyfriend Rupert Friend, and their other co-star Matthew Rhys.

Sienna Miller has defended herself - and fellow party-girls such as Britney Spears and Lindsay Lohan - saying their nights out are no different to anyone else's.

She told OK magazine: "I think everyone's entitled to their own decisions."

"Girls are doing the same thing all over the world as what these girls are doing, but they're not being photographed while they're doing it."

"I think it's healthy for young girls to go out and have fun in their teenage years and early twenties. I'm not going to judge anyone."