The Liberal Democrats will hold their conference at the seaside in Sussex at least three times in the next five years.
In a move worth millions of pounds to Brighton and Hove, the party has booked conferences in 2003 and 2006.
It has already reserved a September date for this year and may also return to Brighton in 2004.
The party is attracted to the city because of its large conference centre and ideal location, close to London and Gatwick airport.
More than 2,000 delegates attend the autumn conference, which also attracts a similar number of journalists, lobbyists, diplomats and visitors.
The decision was confirmed by the party's national conference committee in London on Saturday but is subject to any final negotiations with the council.
Chris Maines, conference chief steward, said: "Brighton and Hove is one of our first-choice venues and we are delighted negotiations are going well.
"Increasingly the number of venues for our party conference is becoming limited because of the growth of the party.
"Delegates certainly enjoy coming to Brighton and Hove and are made very welcome by the local hotels, guest houses and restaurants."
Paul Elgood, leader of Brighton and Hove Lib Dems said: "This is a terrific boost for Brighton and Hove.
"I am delighted the Lib Dems have made such a strong commitment to the city."
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