GuardianWitness, which is available free for iPhone, Android and online, is part of the Guardian's open journalism initiative of diversity and plurality.
"It's a new part of our platform which more deeply integrates the way we want to do open journalism on our sites," Joanna Geary, social and communities editor for the Guardian, told Journalism.co.uk.
"So it allows us to set assignments when we're working on stories that allow us to work with our audience but it also allows our audience to suggest ways they may want to work with us in the future," she said.
Guardian editors will set weekly assignments on a range of topics, while users are also encouraged to contribute to live news, submit their own stories to be followed up by Guardian journalists or simply browse the content submitted by others on the website.
In a blog post announcing the new platform on the Guardian website, Geary explained how the Guardian readership had expanded to all over the world while readers have contributed to some of the biggest stories of the last few years, from MPs' expenses and the Arab Spring to the UK riots and the death of Ian Tomlinson.
Image provided by the Guardian
"I think we've reached a point with technology where it really is the moment for this sort of platform and we know that it's more likely to work and work well," she told Journalism.co.uk. "It's an essential part of our future and we believe that our ability to collaborate and do open journalism is essential in the digital age. That is journalism."
The GuardianWitness platform comes as part of a rising tide in news organisations curating user-generated content on a large scale, both independently, such as CNN's iReport, and using external platforms such as Scoopshot and Newsflare.
"We are in an era when we have more communication tools than ever before in order to reach out to people across the globe," Geary added. "Those people across the globe are reaching out to their friends and other people around the world to talk about stories.
"Bringing the two worlds together and collaborating creates greater, richer, more interesting stories. We become better journalists and we do better journalism as a result when we bring those two worlds together."
Geary said inspiration for the new platform came last year but development occurred over the last two months. GuardianWitness was developed using n0tice, the Guardian's mobile publishing platform, and launched in partnership with EE.
- The Guardian's Matt McAlister will be speaking at Journalism.co.uk's news:rewired conference on Friday (19 April) about n0tice and curation, as part of the opening panel session. Speakers from CNN iReport and Scoopshot will also be speaking at the conference, in a session about participatory communities.