Madrid is gearing up for further protests against what is seen by some as an attack on democracy.
Security is tight; an estimated 1,300 police officers will be on the streets.
Struggling through a recession, many voters feel their country is now unjustly in hock to Brussels.
They plan to surround the Spanish parliament, claiming the financial crisis has "kidnapped" democracy.
A government spokesman told reporters the last time parliament was surrounded like this was during the coup of 1981. "That was a act against democracy she says and so is this." said Dolores de Cospedal, the General Secretary of the Popular Party."It goes against the people's will."
The crisis, blamed on the collapse of a speculation-driven property boom, has plunged Spain into the red, throwing millions out of work and many into poverty.
Tuesday's demonstration is likely to be more tense than this one last Saturday, when more than half a million Spaniards took to the streets of the Spanish capital in a march organised by the main trade unions.
