Hundreds of thousands of people massed in the streets of Barcelona yesterday to call for Catalonia to break away from Spain, two weeks before a regional election that many see as a “make-or-break” moment for the independence movement.

Close to 500,000 people had registered to form a white “human mosaic”symbolising a blank page and the new country they hope to build after the September 27 election, portrayed by local authorities as a proxy vote on secession.

The demonstration took place on Catalonia’s national day or “Diada”, which this year also marked the launch of official campaigning in the northeastern region, which accounts for nearly one fifth of Spain’s output and population.

Not far from the Meridiana, the long avenue where the demonstration was held, 48-year-old interior designer Silvia Palomares said this year’s celebrations were more important than the previous ones.

A failure to achieve an absolute majority of both seats and votes would be a further blow

“This is the definitive year. If we don’t manage to have people going to vote on the 27th, then we’ll suffer,” she said. “The goal is to become independent, because we’re suffocating – economically and emotionally.”

A closely watched survey on Thursday suggested that separatist parties would achieve the slimmest of majorities in the regional parliament, but fall well short of 50 per cent of the vote.

While any outcome, positive or negative, will shape Spain’s political agenda ahead of a December general election, a separatist victory would be highly unlikely to translate into outright secession.

Pro-independence parties have said they will start a “road map”to an independent Catalan state within 18 months if they win control of the regional assembly.

However, the movement has been losing steam since a symbolic referendum on independence last year attracted only two-fifths of the 5.5 million Catalan voters, albeit with 80 per cent in favour of secession.

A failure to achieve an absolute majority of both seats and votes would be a further blow. “After many centuries, we have the great opportunity to vote on our democratic future, so we have to take advantage of this occasion.

Only a clear ‘Yes’ can change things,”said Artur Mas, the head of the regional government.

Spain’s centre-right Prime Minister, Mariano Rajoy, fiercely opposes both the attempts to turn the Catalan election into a proxy vote on independence and the idea of secession itself, which he has called a “nonsense”.

His government has tabled a Bill for the reform of Spain’s constitutional court that would give it enough clout to stop any unilateral declaration of independence.

However, with pollsters predicting that the regional election will leave the Catalan parliament divided, it may simply extend a deadlock between local and national authorities.

Several national parties have said they are ready to discuss a constitutional accommodation for Catalonia after the general election, but would require a consensus that will be hard to reach.

The possibility of such a stalemate is a big concern for companies and investors in the region. Catalan separatists say they would be in a better position to boost the economy if they had their own state and stop tax transfers to Spain’s poorest regions.