Aspiring young British costume and set designers have been encouraged by film and theatre director Sam Mendes to submit their own designs for his hit musical Charlie and the Chocolate Factory.

Mendes – who has won Academy and Olivier accolades for his work – has launched the The Young Theatre Designer Award, which challenges entrants aged 13-21 to bring Roald Dahl’s famous story of Charlie Bucket, Willy Wonka and the Oopa-Loompas to life.

Award hopefuls must submit their set or costume designs for any of the characters or scenes from the musical, along with an explanation of how they work. Ambitious designs for moving sets and special effects are welcomed – Dahl’s story features a flowing chocolate river and waterfall and a flying glass elevator, among many other fantastical elements.

“Creating something out of nothing is miraculous – that's what Roald Dahl did, it's what Charlie Bucket and Willy Wonka do, and it's what we're celebrating with this prize," said Mendes. “When we were creating Charlie and the Chocolate Factory, one of the key things we always wanted to get across was the importance of the imagination.

"At the start of this show, Charlie Bucket's world is grey and cold, but he uses his imagination to transform the world into something wonderful. And Willy Wonka and his factory are the embodiment of the power of imagination.”

A second award, called Charlie's Challenge, has also been launched. It is open to students aged 5-15 and calls for them to share imaginative inventions solving a problem facing their family. Drawings, descriptions, photos and videos will all be accepted.

“Don't worry about what seems possible or not possible,” said the competition organisers in a statement. “Charlie dreams up all sorts of wacky inventions and ideas for his family; marshmallow pillows, ice-cream that never melts and a joke book made from jelly beans.

“Lots of inventions have been made by young people, including ice lollies, earmuffs and the trampoline – so don’t think it’s just adults who can think up new ideas.”

The deadline for entries to both challenges – which have collectively been named the Imagination Awards – is 6 June 2016. A shortlist will be announced on 20 June and the final winners will be revealed on 8 July.

Winners of the theatre design prize will meet the creative team behind Charlie and the Chocolate Factory and see how the show is put together backstage.

Judges for the two awards include Mendes, innovation consultant Sir Ken Robinson, set and costume designer Mark Thompson, London Theatre Society president Caro Newling, structural engineer Roma Agrawal and the Science Museum's first ever ‘Inventor in Residence’ Mark Champkins – the creator of self-heating cutlery, word counting pencils and self-prescribing glasses.