The campaign also aims to position the city as a centre for gay weddings, following the expected law change later this year.
Media targets will include national, international and local news, as well as specialist bridal and lifestyle magazines. The agency is planning PR stunts and media relations. The campaign will run from next week.
The Priory Partnership PR director Paula Seager said: "It is one of the income-generating areas for the council at a time when council tax is going up."
A Brighton and Hove City Council spokeswoman, said: "One reason for this campaign is to promote civil ceremonies in anticipation of the civil partnership regulation."
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