The agency landed the business following a three-way pitch against digitalTMW (the digital arm of Tullo Marshall Warren) and OgilvyOne.
The brief is understood to involve redesigning the EST website, est.org.uk, plus online advertising with a focus on stronger integration with above-the-line campaigns.
The review was not handled by COI. The EST has used COI services in the past, but the COI digital roster is currently under review.
Online media buying, handled by i-level, is unaffected.
In March 2005, the EST appointed Mustoes and TMW to its through-the-line account. Eight months later, the organisation launched a £5 million integrated TV, press and online campaign that encouraged the public to reduce its daily energy consumption by 20 per cent. A key component of the campaign was a website, saveyour20percent.co.uk.