Ahead of the non-binding referendum on independence next month, the 'no' campaign is all but invisible on the streets of this port city

Carles Castillo can't win. In Catalonia the outspoken local politician is derided as a feeble sellout for opposing total independence; in the rest of Spain he is damned as a rabid separatist for wanting a bit more self-governance.

"I feel like I am being bombarded from both sides," says Castillo, strolling through the port district of his much-loved home city, Tarragona, where he is keen to point out a Roman amphitheatre, a fleet of fishing boats and the busy harbour beyond.

Fast-growing separatist sentiment in Catalonia has risen to fever pitch with the prospect of a referendum on 9 November, even though the results would be non-binding and the poll is technically on hold while the national constitutional court decides if it is legal. On crash barriers and underpasses in provincial towns and on banners in the heart of Barcelona, graffiti in the Catalan language demand "Liberty for Catalonia". In September more than 1.8 million people turned out for a march demanding independence.

Activists collecting money in a caixa de resistència (resistance fund) have turned Barcelona's Plaça de Catalunya into a venue for concerts and meetings, and balconies across the region are festooned with the red-and-yellow stripes of the Catalan regional flag.

This public fervour has been matched by a hardening of Madrid's already stern opposition to any change in Catalonia's status, leaving a dangerous chasm of incomprehension between the two sides, and moderates such as Castillo feeling despised by all.

Support for independence has more than doubled since the economic crisis began. Even so, polls show that more than half of Catalans still back either the status quo or a stronger version of autonomy that stops short of a full exit from the Spanish state. But there is little public evidence of these voters. And there is almost no sign of a Catalan equivalent to Scotland's Better Together campaign – no posters, concerts or high-profile donors. Some opponents of independence worry that, because the debate is so polarised, a large slice of the population is being intimidated into silence. The bestselling Catalan author Javier Cercas wrote in a recent article for the Spanish newspaper El País: "It is possible that recently in Catalonia we have been living through a kind of 'soft' totalitarianism ... the illusion of unanimity created by the fear of expressing dissent."

Cercas rose to fame with Soldiers of Salamis, a book about the civil war, and perhaps because of his research into Spain's turbulent history, he considers independence a dangerous gamble. "I like adventures in films and books, not in politics," he has said in the past.

The pro-independence alliance that leads the regional government denies that its opponents are being stifled. "Some people talk of fear, others of shame, but this is not the problem at all. We have an absolute respect for people," said Josep Rull, general coordinator of Convergència i Unió. He stressed that the government called the November referendum to give all Catalans a voice, and would respect a rejection of independence just as Scotland did. "The only way to find out if we have a silent majority is to have a vote," he said, sitting in his imposing office at the regional parliament, an 18th-century building overlooking a lush park.

He said his party was determined to go ahead with the poll, even if it meant defying Spain's constitutional court, which Rull dismissed as biased. "On 9 November, I believe that one way or another there will be ballot boxes."

If the poll goes ahead, it might boost the tiny and fragmented opposition. Perhaps because it is only mobilising now, there seems little awareness of how the Better Together campaign scraped to victory in Scotland. For those unafraid of speaking out, there are no posters to put in windows or designs to copy for banners. There are no people travelling from other parts of Spain to beg Catalans to stay, and activists scoffed at the idea of a solidarity march in Madrid like the Let's Stay Together rally that drew thousands to London.

The only prominent anti-independence group is Societat Civil Catalana, an organisation officially established only this year. Founding member Rafael Arenas, a law professor at Barcelona's Universidad Autónoma, said that until recently campaigning simply had not seemed necessary.

"A portion of the population has always been pro-independence, but most people felt it was a minority group, and we would never really reach the point of secession. That changed in 2012, when the president of the regional parliament declared his support for independence. You can't say it's marginal when you have the institutions of government behind it. Things have changed radically."

Arenas was already touching on the subject of independence in blogs last year, warning of the economic risks, and that an independent Catalonia could be left stranded outside the European Union – something pro-independence groups contest. Then friends suggested the logical next step was to form a group to unite Catalans who want to stay part of Spain.

He says that opponents are always polite to his face, and though he gets abuse online he shrugs it off: "That is what social media is like for anything." Still, he admits some are afraid of speaking out. "I can't say whether its justified or not, but I had a colleague in my office recently saying, 'I agree with you, but I can't speak out'."

Perhaps because of this, progress is slow. On Catalonia day last month, a public holiday when Barcelona was packed with pro-independence demonstrators, only a few thousand joined a pro-union parade in Tarragona organised by Societat Civil Catalana. Castillo was among the small crowd, balancing his fears about rightwing extremists who might attend with his conviction that he needed to take a stand when so few others were: "I had my doubts. I don't like to be marching beside fascists. But in the end I decided I had to plunge in."

For him, the rest of Spain is about much more than the government in Madrid. His parents were born outside Catalonia, he spent childhood holidays with close-knit family in the south, and feels a strong bond with the home of heroes such as poet Federico García Lorca, killed by the pro-Franco nationalists during the civil war. "I have family ties, emotional ties to Spain. I believe there is another Spain beyond the one we see, a progressive, leftwing Spain which perhaps has been quieter, but it's there. It seems quite selfish to me to leave this Spain alone."

Support from elsewhere in Spain for Catalans keen to stay inside the union has been conspicuous by its absence. There has been nothing to match the English pleas made to Scottish voters. The only Spanish voice heard in Catalonia is that of the Madrid government, which seems oblivious to the implications of the groundswell of pro-independence sentiment, much as at Westminster politicians missed the shift in Scottish opinion until just before the referendum. "All we receive is threats and menace," Rull said. "You can't simply ban, ban, ban."

Catalans say their distant rulers are patronising and dismissive, citing the education minister who called for the "hispanisation" of education in the region, which resembled for some the much-resented Franco-era bans on the Catalan language and even names.

"Every time [prime minister] Mariano Rajoy opens his mouth, 200 Catalans convert to the separatist cause," Castillo said. "If things carry on this way, even I can imagine becoming pro-independence myself."