With nearly 300 workers in court over their participation in strikes, Spain's major unions are fighting back, launching a campaign against what they call the increasing "criminalisation" of strikes and other labour activities.

At least 260 workers across Spain are facing cumulative jail time of 120 years over their participation in recent labour activities, said Cándido Méndez of the UGT general workers' union.

Threatened sentences range from fines to three years in jail. The moves is set against a backdrop of a recent labour law reform that made it cheaper and easier for companies to lay off people, reduce wages and modify the conditions of employment. "It's creating a dynamic in which the clear aim is to discourage workers from mobilising," Méndez said.

Prosecutors are exploiting an obscure article in the criminal code meant to prevent workers from being pressured into striking, said Ignacio Fernández Toxo, who heads the Workers' Commission trade union. The article is being increasingly relied on to justify fines and time in jail for those who strike.

The result, he said, was chilling. "They're trying to make examples of a few, instil fear and discourage people from participating in mobilisations and strikes. We're talking about a fundamental right that's enshrined in the Spanish constitution."

As part of the campaign, letters are being sent out and meetings planned with prosecutors and government officials. Rallies are also being organised across Spain next week.

The issue takes on particular importance, said Toxo, when Spain's recent history is factored in. It was not that long ago that Spanish workers lacked the freedoms to claim their rights as workers, he pointed out.

"We thought we had clearly overcome this phase in Spain. But it seems like maybe not."