Flicking through the rails at high street store Monki, teenager Hanaa Maqbool swiftly picks out two looks she is considering wearing for Eid; one is a floral jumpsuit with wide sleeves and even wider legs that she wants to match with a palm-print headscarf. The other is an oversize lemon print dress that she’ll wear with cropped white jeans.

“My sister is nine years older than me and she always says she never had the choices I do when she was growing up because covering up wasn’t as easy then,” she laughs. “Mum would always get her really nasty, bland Eid clothes – old-lady clothes – but the high street has cottoned on to fashionable Muslims. We’re in now.”

Maqbool says she doesn’t mind modest fashion being a trend; she is simply grateful for the choice. This is a look that embraces clavicles over cleavages and hemlines that hang low rather than hike high. “It’s not about it just catering for Muslim girls,” says Maqbool. “Lots of girls dress this way because it just looks cool.”

Maqbool’s analysis is a fair summary for anyone with an eye on fashion; the prevailing silhouette of the decade has been voluminous sleeves and cocooned silhouettes – loose, comfortable, chic looks that brands like Arket, Cos and Weekday have used to build a significant fanbase. It’s a style that has trickled down to the high street from high fashion and, crucially, from powerful female designers running influential labels.

Jil Sander and Margaret Howell may have long favoured simple lines and boxier fits but arguably it is Phoebe Philo, the designer’s designer, who has had the most significant impact. Her work – first at Stella McCartney, later when running Chloé, and most significantly at Céline – favoured practical, functional pieces designed for getting things done. The proliferation of polo necks, white trainers and straight-cut trousers in our wardrobes are pure Philo.

Facebook Twitter Pinterest Ghizlan Guenez, left, and supermodel Erin O’Connor. Photograph: Darren Gerrish/WireImage

And so, when Victoria Beckham set up her fashion house over a decade ago, few could have predicted that the pioneer of Wag culture, trademarked as it then was by bouncy hair and bodycon, would follow suit and become an enduring influence on modest fashion. But next month, Beckham – alongside Valentino and Burberry – will be selling on The Modist, a luxury retailer that has become the Middle East’s answer to Net-A-Porter: a high-fashion edit of runway looks tweaked and styled for modest dressers.

Its founder, Ghizlan Guenez, launched her company on International Women’s Day two years ago, under the tagline Modest Fashion, Modern Thinking. She has been working with western designers wanting to tap into the market since the very beginning. “Lots of designers are catering for the Middle East now: it’s a significant area of growth,” she says. “But where modest dressing might be a mood for the moment, the desire for women dressing this way all the time won’t diminish.”

While Muslim women are assumed to be her biggest customers, she says the highest demand actually comes from clients in Texas. “It’s not about religion or faith necessarily,” she says. “So many women want, say, their dresses with sleeves, or to be more comfortable without compromising on looking stylish.”

Even Tom Ford, who made his name pushing the notion that “sex sells” to its limit in the 1990s, has caught on. At New York fashion week in February, he debuted a collection of high necklines and layered knits. “Fashion is supposed to be, and should be, a fashion designer’s perception of where we are culturally, and now is not the time for super-sexy clothes,” said the man who, while at Gucci, ran an advert in which the brand’s logo was shaved into a model’s pubic hair.

Headscarves and hijabs have also been de rigueur at the shows. Gucci, Max Mara, Molly Goddard, Versace, Calvin Klein, Marc Jacobs and Chanel have all sent models in “Muslim-ish” headpieces down the runway. The argument that the industry is offensively fetishising religious wear, turning something deeply meaningful into a throwaway trend, has been made several times. On the other hand, by seeming to be more inclusive, is this progress?

Author and influencer Yassmin Abdel-Magied is circumspect: “I think modest being fashionable right now isn’t really about modesty: it’s about trends. In the same way skin was fashionable in the 90s, in times it’ll be unfashionable again. [But] there is something beautiful about the way cultures with modest traditions style themselves, so there is rich, untapped stimulus for fashion houses.”

It helps, of course, that it’s also where the money is. According to the World Economic Forum, 40% of people living in the Arab world are millennials with higher spending power than their peers everywhere else, including the US. According to Alison Loehnis, president of Net-A-Porter, the region has “a much higher percentage of Extremely Important People than the rest of the world, at 12%” which is four times the global average of 3%. In addition, 71% of all sales in the Gulf come from mobile devices, compared to the global average of 50%. As Loehnis puts it, “the Middle East is on the frontier of change” and the influence of Muslim consumers on trends can only grow.

Demure, it seems, really is more. Last month, the American-Somali model Halima Aden kicked off Ramadan by delivering a sensational PR coup for Sports Illustrated. The 21-year-old, who grew up in a Kenyan refugee camp, became the first woman to pose in the US magazine’s annual swimsuit issue wearing a hijab, a burkini and a massive, cheesy smile. As an image, it was contrived to be talked about; a headline-hungry twist for a magazine geared towards the male gaze. Aden, who made her debut as a hijabi model just two years ago, declared it “a dream come true” and “another tool to really uplift women in my community”.

Meanwhile, last week Dove added a new string to its inclusive bow with the launch of a campaign featuring a woman in hijab declaring “modesty is beautiful”. On Twitter, a backlash rumbled with one user tweeting: “Well done @Dove appropriating a cloth that is used to subjugate women. Millions around the world have been forced into it because dare they try to go free without it. Why does modesty depend entirely on women? Why is modesty beautiful? #FreeFromHijab.”

One view is that the modest look has swamped the high street with 1970s Laura Ashley-style frou-frou. “Floaty” is the polite term for what even on a pretty model looks frumpy, gussied-up, constrictive and itchy, says one commentator.

“It’s not a zero-sum game,” says Abdel-Magied. “Folks can and do have legitimate issues around women’s right to choose what they want to wear, but one can fight those without simultaneously denying women who want to dress modestly the freedom to do so without judgement. [For Dove to] say it’s beautiful does not inherently imply it’s better than any other way of being. It’s about seeing the plurality of experiences and possibilities in the world. For me, my choice of clothing is how I want to move through the world. My modesty centres me, that’s why it’s beautiful to me.”