Up to a million people are expected to converge on Barcelona to join a rally demanding independence for Catalonia in Spain's north-east.

At least one train and more than 1,000 coaches have been chartered to bring supporters to Tuesday evening's march, which is likely to mark a watershed in the hitherto marginal independence movement and a rupture with Spain's federal government.

Long-standing resentments about what Catalans see as their unfairly high contribution to central government have been inflamed by Spain's economic woes. Polls show support for independence running at 51%, twice as high as in 2008 when the financial crisis began.

Map of Catalonia

Carles Brugueras, a documentary film-maker, said he was not a nationalist but favoured independence from an economic perspective. "For a long time, Catalonia has been generating a lot of resources for Spain but the fiscal balance has been very unfair," he said.

Laura Nuñez, a law student, is also a new convert to independence, believing it would boost the Catalan economy.

"We're economically the most powerful part of Spain because of industry and tourism and we contribute more than other Spanish regions.."

The rise in support for secession has caught Catalonia's nationalist CiU government off guard. CiU, which has governed the region for 25 of the 33 years since democracy was restored after the death of the dictator Franco, has never aspired to independence, preferring to wring more autonomy out of minority governments in Madrid.

Artur Mas, the Catalan president, initially said he had no intention of joining the march but now says he will attend in a personal capacity. An attempt by another senior CiU politician to justify his attendance at the rally by portraying it as pro-Catalan rather than pro-independence fell flat when Carme Forcadell, spokeswoman for the group behind the march, said: "Anyone who attends should understand that they will be considered pro-independence."

Catalonia is one of 17 autonomous regions in Spain's federal system, which has come under attack from, among others, the European Central Bank, who have questioned the system's viability. Most of the regions have been run as virtual fiefdoms by local politicians hand in hand with the savings banks, almost of all of which are now bankrupt. Earlier this month, Catalonia asked Madrid for a €5bn (£4bn) bailout, while claiming that it was only asking for what was rightfully its own in the first place.

There is considerable antipathy in Spain towards the Catalans, who are often viewed as complaining and, from a Spanish point of view, disloyal. Catalans are, understandably, hurt by this. "I'm fed up with the way we're criticised whatever we do," said Gemma Soler, a secretary. "And I'm tired of having to justify myself wherever I go in the peninsula, that we're not the extremists they make us out to be, as if we went around burning cars and flags all the time."

Montse Agell, who works for a charitable foundation, said one of the reasons she was pro-independence was that "basically, I don't want to live among people who don't like me".