have marshalled their millions of fans to back a charity campaign.
The four-piece, said to be worth around £25 million each after topping the charts worldwide since emerging in the 2010 series of X Factor, have asked fans to share pictures and videos online describing the kind of world they want to live in as part of the action/2015 campaign.
They said: "Time and again our fans have shown how creative and powerful they can be when they unite and that's why we want to all join together to speak out and hopefully make a real and lasting change to the world around us.
"Young people really do have the power to help end poverty, tackle inequality and to stop dangerous climate change.