Linstock Communications was awarded the three-year contract by the Office for National Statistics after a six-way pitch managed by the Central Office of Information.
The agency's work will form part of a nationwide PR campaign to highlight the census and encourage people to fill in and return questionnaires on census day - 27 March 2011.
Linstock director Jon Bennett will report to 2011 Census head of marketing Oliver Doerle. Bennett said: 'The census is quite esoteric and time-consuming. We're trying to overcome these barriers by thinking about the huge impact this will have on people's families for years to come.'
Linstock will promote the census by visiting schools and community centres with a high concentration of ethnic minorities, and leafleting around city centres.
One of the objectives of the census is to provide accurate population statistics, which are used to decide the allocation of funding for local authorities. The census takes place every ten years.