Puigdemont’s pro-sovereignty administration insists the wealthy north-eastern region has a political, economic and cultural right to self-determination.
But the Spanish government is implacably opposed to secession, arguing that it is a violation of the constitution, and has vowed to use all possible means to stop the referendum from being held.
Puigdemont said that Madrid had left his government with no choice but to call the vote.
“When they’ve asked us what we Catalans want, we’ve given them proposals - all kinds of proposals,” he said. “But they have all - without exception - been rejected or seriously cut back.”
Spain’s deputy prime minister, Soraya Sáenz de Santamaría, dismissed the announcement as an empty threat, saying: “They can announce a referendum as many times as they want and put it back as many weeks as they want, and hold as many events as they want, but the referendum is not going to take place.”
More than 80% of participants opted for independence in a symbolic poll held three years ago – although only 2.3 million of Catalonia’s 5.4 million eligible voters took part.
This time round, however, the Catalan government insists the results will be legally binding.
In a speech in Madrid last month, Puigdemont said his government had a “democratically inviolable” commitment to the referendum and accused Spain’s prime minister, Mariano Rajoy, of failing to do anything “serious, sincere or real” to resolve the issue.
Spain’s constitutional court ruled the previous referendum was illegal five days before it was held on 9 November 2014, but the then Catalan president, Artur Mas, and others pushed ahead with the vote, helped by more than 40,000 volunteers who opened schools and installed polling stations.
In March this year, Mas was found guilty of disobeying the constitutional court’s ruling and banned from holding public office for two years.
Puigdemont has said that he is prepared to face the consequences of defying the court.
“This is a deeply serious business, and profoundly democratic,” he told the Guardian last year. “I could not disobey the will of the Catalan parliament.”
The Spanish government, however, is confident that it can stop the referendum from happening in the first place. As well as the courts, it has the power to invoke article 155 of the constitution, which would allow it to take drastic steps to thwart the vote by suspending regional autonomy.
Such a move could see Madrid ordering the closure of schools in the region to stop them being used as polling stations and even taking control of the Catalan police.
Last week the Venice Commission – a panel of experts who advise the Council of Europe on constitutional law – wrote to Puigdemont, telling him that the referendum would have to be carried out “in agreement with the Spanish authorities … and in full compliance with the constitution and the applicable legislation”.
Although the separatist movement has acquired huge momentum over recent years, any vote is likely to be very close.
According to a poll at the end of March, 48.5% of Catalans oppose seceding from Spain, while 44.3% support breaking away.
The opposition camp appears to be growing: another poll, from December last year, revealed that 46.8% of Catalans were against independence, compared with 45.3% in favour.
On Sunday, the former Barcelona football club coach Pep Guardiola will read out a manifesto in favour of a referendum at a rally in the city.
He told Radio Catalunya that the region needed the opportunity to decide its own future, adding: “We’re just asking that people be allowed to vote for a better life.”
More about: #Catalonia