Up to 10,000 are expected at a peace march against globalisation in the city centre on Sunday.
It may be the biggest in Brighton and Hove since a Right to Work protest outside the Tory conference 20 years ago.
Sponsored by anti-capitalist group Globalise Resistance, the Green Party and Socialist Alliance, it is attracting support from unions, community organisations, peace campaigners and politicians.
The rally and march starts at noon on The Level.
Speakers confirmed so far are Alan Simpson MP, Euro MP Caroline Lucas, writer George Monbiot, Luca Casarini, Oscar Olivera and city councillor Keith Taylor.
Coun Taylor said: "We have worked hard to deliver a protest that gives ordinary people the chance to voice their concerns over the way New Labour has stopped working in their interests, and instead seems to be forging ever closer ties to big business."
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