The M&S Do Your Thing campaign, premiering tomorrow night during Britain's Got Talent on ITV1, encourages parents and guardians to upload videos demonstrating their child's passion or talent onto an ITV.com minisite.
Developed in collaboration with photographer Rankin, the TV ad features young people modelling the retail chain's summer collection, while also playing a variety of roles including a beatboxer, street dancer and astronomer.
Parents and guardians will be invited to put their children forward to appear in M&S's next ad campaign for the autumn/winter kidswear collection.
The competition, which opens tomorrow and closes on May 23, will be judged by Rankin and Alex Kelly, M&S Kidswear marketing manager. The winners will be announced at the same time as the Britain's Got Talent final.
Karl Doyle, M&S director of Kidswear, said: "We're really excited to be working with ITV and Rankin on this nationwide search in what is a totally original and unique campaign.
"We want to encourage kids to 'do their thing' and get involved in the next campaign as well as inspiring them with our on trend, high fashion kidswear ranges."
The Marks & Spencer childrenswear campaign will run on television, print, video on-demand and digital media.
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