The agency won the business after a shootout against Wheel and Harvest Digital.
Work carried out by Designate includes two campaigns focusing on the seaside city's small hotels and winter breaks.
The small hotels campaign, which has now launched and is running on the Adlink network, includes a two nights for the price of one offer using banner advertising to focus on different hotel themes such as luxury and romance, seafront hotels and individually themed bohemian rooms.
The winter campaign launches in November and runs for five months.
Duncan Oakden, Designate senior media planner/buyer, said: "Working closely with Adlink has made it possible for a prime selection of sites which have historically performed well for travel and tourism clients."
is run by Brighton and Hove City Council.
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