BARCELONA, Catalonia (AFP) -- As Catalans rallied Wednesday for a dramatic 400-kilometre (250-mile) independence protest, their zeal to break from the rest of recession-hit Spain was being fed by deep resentment over Madrid's economic policies.

Many in Catalonia, renowned as Spain's industrial heartland, hold a grudge against the Spanish government, which they accuse of imposing unfair taxes and failing to fulfil promises of public investment.

Catalan regional president Artur Mas protested the "unjust" economic system in an opinion piece for the New York Times before the region's September 11 national day, or Diada, when activists joined forces aiming to form a 400-kilometre human chain of hundreds of thousands of people.

"Catalonia now receives less public expenditure per capita than more than half the other regions of Spain, though we contribute far more than average," Mas wrote.

"In addition, the Spanish government has failed to carry out its investment obligations," he said.

It is a widely held sentiment in this region of 7.5 million people where the unemployment rate is 23.85 percent -- lower than the national average of 26.26 percent but still painfully high -- and the public debt amounts to 50.9 billion euros ($67 billion).

Further stoking ill feeling, Catalonia had to go cap in hand to Madrid in January to ask for 9.07 billion euros from a fund to help debt-laden regions.

At the Port of Barcelona, one of the largest on the Mediterranean, 36-year-old truck driver Daniel Artigas complained of over-investment in other parts of Spain on items such as high-speed train services and regional airports that remain unused.

"It's not right that they spend money on airports or trains that go empty and not the Port of Barcelona," Artigas said.

A Catalan regional economic spokesman said the Spanish government had failed to carry out 5.7 billion euros in promised investment in infrastructure.

But a spokeswoman for Spain's public works ministry said Madrid had invested 21.6 billion euros in infrastructure from 2000-2012, with another 1.12 billion euros to be ploughed in this year -- 2.6 times the average for other regions.

Catalonia's government accuses Madrid of collecting 16 billion euros more in taxes than it spends in the region each year.

"There is a general feeling that many of Catalonia's problems are due to Spain's ill-treatment in the economy, taxes and infrastructure," said Ferran Requejo, political scientist at the Pompeu Fabra University of Barcelona.

The Barcelona port is a case in point, waiting for years for the promised construction of new railway lines to prevent a transport bottleneck.

After Spanish Prime Minister Mariano Rajoy and Catalonia's Mas held closed-door talks last month to ease tensions, an agreement was reached last week between the port and Madrid.

Under the deal, new rail lines are to be completed in 2015 in a 100-million-euro investment to be cofinanced by the Spanish government and the port.

"When you want to resolve problems there is always a way," said Mas as the port agreement was signed on September 4 after months of stalemate in negotiations, urging Madrid to "follow the example" in other areas.

"The existing rail links have major deficiencies," said Sixte Cambra, president of the Barcelona port, through which record exports moved in the first half of 2013.

The new rail lines "are important to make our port's logistical chain more competitive and for our development," said Cambra from his office, with windows overlooking the sun-drenched port where containers were unloaded and tourists disembarked from cruise ships.

But not everyone blamed Madrid for all of Catalonia's woes.

"What we should be asking is how the money is being spent in Catalonia.

Twenty years ago we were the richest region and now look at us," said 41-year-old driver Jose Miguel Saez, taking a rest by his truck.

"I am sure some money has stayed in Madrid but I am also sure that it's not as much as they tell us here," he said, before getting back in the truck to pick up his goods.