“We are stronger if we can act in a cross-party, united way, across the whole ideological spectrum,” said Puigdemont, addressing the event in Barcelona via video link from Germany, where he faces extradition to Spain.
Unlike other separatist movements such as in Scotland, where separatism is concentrated in the Scottish National Party, Catalonia's separatists are split among Puigdemont's conservatives and progressive and radical left factions.
They united behind a movement that culminated last October in the regional parliament's declaration of independence.
But the conservative Spanish government in power at the time, headed by Mariano Rajoy, responded by sacking his government, suspending the Catalan parliament and imposing direct rule over the region.
Madrid lifted direct rule in June after a new president was installed, Quim Torra — also a separatist and close to Puigdemont.
Puigdemont and four of his ministers fled to Brussels to avoid facing charges including rebellion related to their push for secession.
He was detained while travelling in Germany. A German court last week gave the green light to Puigdemont's extradition for misuse of public funds but not the more serious charge of rebellion, which carries up to 25 years in jail.
German prosecutors are now to decide whether to transfer him to Spain.