There were chants of “Puigdemont, president” from the crowd that was estimated by police to number 45,000. Many people were draped in Catalan flags; some carried placards criticising the European Union for not putting pressure on Madrid. One sign showed the face of the European commission president, Jean-Claude Juncker, with the question: “Democracy? Some defend it when it suits them. Shame on them.”

Puigdemont, who like many in the crowd wore yellow in support of jailed separatist leaders, addressed the crowd in Catalan before switching to French to direct a message to Juncker.

“Is there any place in the world that holds demonstrations like this to support criminals?” he said. “So maybe we are not criminals. Maybe we are democrats.“

Spain’s supreme court withdrew an international arrest warrant for Puigdemont on Tuesday in order to bring his case back solely under Spanish jurisdiction, leaving him without an international legal stage to pursue his independence campaign.

Puigdemont and four of his cabinet members fled to Belgium when Madrid imposed direct rule on Catalonia and sacked his government after the 27 October declaration of independence.

He is likely to be detained if he returns to Spain, pending investigation on charges of sedition, rebellion, misuse of public funds, disobedience and breach of trust.

Puigdemont said on Wednesday he would remain in Belgium for the time being.

“Brussels is a kind of a loudspeaker for us,” said Gloria Cot, a clerk from Barcelona at Thursday’s march. “It is a loudspeaker so that people can know that we really don’t have a 100% democracy in Spain and that Catalonia has always been subjected to problems with Spain.”

Juncker’s deputy, Frans Timmermans, said he welcomed the “very positive atmosphere” of the demonstration, which took place as campaigning gets under way for the 21 December Catalan election.

The Spanish prime minister, Mariano Rajoy, hopes pro-independence parties will lose their majority in the Catalan parliament to end the deadlock created by his government’s refusal to recognise the banned independence referendum Puigdemont held in September. Polls have separatists and unionist parties in a tie.

Timmermans said there was no change to commission policy that the dispute with Catalan authorities remains an internal one in which the EU has no need to intervene because Spain’s democratic constitution is functioning in line with EU values.

He accused Puigdemont and his allies of undermining the rule of law by choosing to ignore a Spanish constitutional ban on secession rather than trying to change the constitution.

“If you do not agree with the law, you can organise yourselves to change the law or the constitution,” he said. “What is not permissible under the rule of law is to just ignore the law.”

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