Nearly half of the UK's video game players are women, and now they are designing and writing them too, including top sellers Gears of War 3, and Deus Ex: Human Revolution. What took them so long?

Three of the biggest video game releases this winter have something unusual in common. Gears of War 3, featuring space marines fighting aliens, Uncharted 3, an Indiana Jones-inspired game, and Deus Ex: Human Revolution, a dark science-fiction adventure, were all written by women.

According to research by Tiga, the trade body representing the UK games industry, women make up just 12% of the development workforce in Britain – a percentage reflected by similar surveys in the US and Canada. Why? The obvious answer is that, because games were born in dingy arcades and on 80s home computers, creators tended to hail from computer science and engineering backgrounds, areas traditionally dominated by men. "Women have, of course, always played video games, but in the past it was always as a minority. Yet a report by the Internet Advertising Bureau in September found that 49% of gamers in the UK are female; but that percentage is not being reflected in the makeup of the industry, particularly at senior levels.

Mitu Khandaker, who started programming at the age of 12 and now runs her own indie development studio, Tiniest Shark, credits "a complicated mix of marketing, early arcade culture, and deep-seated cultural expectations" for the status quo. "There are a lot of things in games that women can point to and go 'this isn't for me', whether that's eye-rollingly sexualised female characters, or just the openly misogynistic attitudes to be found within many gaming communities."

As an example, Khandaker refers to a recent controversy involving the zombie horror adventure Dead Island, in which gamers scouring an unfinished version of the game found a line of code referring to the female character as a 'feminist whore'. "It boggles the mind," she says.

Deus Ex: Human Revolution: 'about technology's threat to humanity'.

Since its launch in 2008, the Nintendo Wii console has widened the appeal of games enormously by concentrating less on shooters and more on inclusive social experiences such as Wii Sports and Wii Play. At the same time, music titles such as Rock Band and Singstar have brought games into pop culture, and massively successful Facebook and mobile titles such as Farmville and Angry Birds have attracted people who might never have bought a console. As the audience widens, so does the pool of potential development staff.

"The consoles we had at home were mainly my brother's – I wasn't a huge gamer," says Siobhan Reddy, studio manager at Guildford-based developers Media Molecule. "But when I was a teenager I was really into making fanzines and little movies, and I saw how technology and the arts were beginning to fuse together. When the games industry was mentioned to me I thought: 'Yeah, that's interesting.'"

Reddy reckons that games development is becoming more appealing to girls as a potential career because it is no longer about a computer sitting in the corner of the room, it's about phones, laptops and social networks. "I look at the generation of young women coming through school now and they've all grown up with technology, they've grown up in an era where entertainment, games and music are interconnected."

Amy Hennig, the creator of the hugely successful Uncharted series, played games as a child in the late-1970s, but then left them behind as a teenager.

Like Reddy, she arrived at game development through a background in other story-telling media. "In 1989, I had an opportunity to do art, animation and design for an Atari 7800 game," she recalls. "At the time, I was purely trying to earn money to pay my way through graduate school in Film Theory and Production – but this rekindled my love for games, and I realised that there were more creative opportunities in this young, pioneer medium than in the more established film industry.""I've been attending the Game Developers Conference for the past three years," says Khandaker. "But this year was the first time there was a line for the ladies' loos. That was a nice – though inconvenient – sign of progress."

Plenty of female designers are bucking stereotypes, working, not just on family-friendly Wii titles, but on action adventures, filled with shoot-outs and fistfights. They do seem, however, to bring in comparatively more rounded characters and twisting, tricky narratives. One of the muscle-bound marines in Gears of War 3 is almost destroyed by grief for his dead wife, while Deus Ex is all about technology's threat to humanity. This is not the stuff of robotic characters and B-movie plots. Perhaps as a result of that, the games have built a strong female fanbase.

Mary DeMarle, the co-writer of Deus Ex, who was an aspiring fantasy and sci-fi author before entering the industry, says: "We bring an altered perspective, I suppose, a different way of looking at things. And the more women become involved in games, the more that will filter into them."

Women developers have certainly been key in experimenting with game design. The LA-based studio thatgamecompany has produced unique, and beautiful PlayStation titles such as Flower, in which players guide a breeze as it collects and disperses seeds, and Journey, an adventure set in a mysterious desert, where participants must forge anonymous relationships with other online players.

The company was co-founded by Kellee Santiago, who had previously studied theatre at NYU; hers is a unique approach to design. "We begin by asking what is the mood or emotion we want to express in a video game. Then we go about discovering what are the mechanics, the visuals, the audio we need for that."

Gears of War 3: muscle-bound marines, but with a sensitive side.

Kellee and fellow thatgamecompany producer Robin Hunicke have become highly influential to young women looking to enter the industry. "They are loved for their creativity and great design, and for putting those things above the assumed desires of a target market," says Kate Killick, a graduate of the University of Newport's game design course and now an artist at startup studio Angry Mango. "Both of those women are active in supporting others and promoting creativity in the industry – I saw Hunicke speak the first time I went to the GameCity festival in Nottingham, and it gave me a lot of inspiration both as a female in the industry and an indie developer."

Killick represents a new generation that resists the notion that the games industry is a boys' own club. "I see a lot of it as unacceptable," she says. "All the over-sexualised female characters, hiring women to 'decorate' stands at games events. I don't think this stuff has a place in the future of the industry."

As interesting as Deus Ex, Uncharted and Gears of War 3 are, they still feature men in the central, playable roles; the anatomically impossible fantasy creature Lara Croft remains the high watermark for female lead characters – and that has to change. Perhaps when the percentage of women in development increases, it will.

"I think young girls need to have their eyes opened to the different avenues open to them in games," says writer Rhianna Pratchett, who has worked on several titles with strong female leads including Heavenly Sword and Mirror's Edge. "They can be artists, animators, writers, designers, producers, programmers … We need to get them fired up about technology and find the Ada Lovelaces of the future. I think both the industry and the educational system have a role to play to achieve this. There are so many great female role-models within the games industry, but they rarely get the exposure they deserve."