The two digital agencies join interactive media production firm Intelfax on the roster. The appointments follows a pitch and tender process that saw more than 100 agencies apply for a place.
The way that and will split the work has not yet been revealed.
Projects lined up by the next year include the redesign and development of its main site. There will also be work on the World Environment Day project, a global event that takes place in June. It aims to encourage the public to take part in activities to improve the quality of life and raise money for environmental causes.
Simon Ashley, internet manager for the Environment Agency, said: "We are facing some big challenges over the next few years, in particular with the convergence of electronic services, and we needed agencies with the right mixture of skills in design and marketing to support us through this process."
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