In the contest, which is part of the Radio Advertising Awards, advertisers and their agencies can submit creative for a new radio ad to win £500,000 of airtime across the commercial radio network.
There is an additional prize of £500,000 worth of airtime for the best existing radio ad.
The closing date for entries is 30 June and the winners will be announced at the Radio Advertising Awards on 17 September at The Room on London's South Bank.
Simon Redican, the managing director of the RAB, said: "We're excited about the introduction of the creative challenge, which is looking to inspire great radio advertising; not only does the client benefit from huge exposure, reaching more than 31.5 million adults a week, but each winning creative team also walks away with £20,000 cash."
This year's Radio Advertising Awards include the GCap Media Planning Awards and the Aerial Awards.