The competition is open to all UK charities, but is particularly aimed at those that have forthcoming media campaigns and would like to increase their print and online media coverage.
The prize includes consultancy and advice from the agency and three hours' support from a professional photographer and videographer.
To enter, charities are asked to complete an application form saying what they do and how they would benefit from the prize. There is no charge to enter.
Claire Southeard, managing director of TNR, said: "We are very proud to initiate this competition and hope we can offer some much-needed support and guidance to a very worthy cause."
The deadline for entries is 16 April.