Spanish unions have called a general strike in response to labour market reforms due to be unveiled by the government on Wednesday.
The unions announced the strike would take place on 29 September, to coincide with a European "day of action".
The government is pressing ahead with the reforms after two years of talks with the unions broke down.
They are supposed to help the economy recover after a deep recession and a surge in unemployment to more than 20%.
UGT union leader Candido Mendez said the changes would favour businesses and "will harm the rights of workers."
They include measures to enable employers to hire and fire more easily.
Test for Zapatero
After the failure of talks, the cabinet is expected to pass the measures on Wednesday and then put them to parliament on 22 June. The measures will take force immediately though the government has not ruled out amending them afterwards.
The general strike will be the first since Socialist Prime Minister Jose Luis Rodriguez Zapatero took power six years ago.
Last week Spaniards marched against a 15bn-euro (£12.5bn) programme of austerity cuts.
However the rallies were smaller than many expected, which Spanish analysts said would encourage the government to press ahead with its reforms.
Spain, like many European economies, is trying to boost growth while simultaneously bringing a runaway deficit under control.
It is one of the countries thought vulnerable to a Greek-style debt crisis, if its repayments become unaffordable.
The Spanish government and the European Commission were on Monday forced to deny reports that Madrid was seeking an EU aid package.
Meanwhile the Spanish treasury secretary admitted that foreign banks were refusing to lend to some Spanish banks.