Leftists and civil rights activists have labeled the bill the "Kick in the teeth law" because it penalizes a battery of protest measures in what they say is a disregard for democracy in a country that only emerged from right-wing dictatorship in the late 1970s.
But Prime Minister Mariano Rajoy, whose People's Party (PP)has an absolute majority in parliament, has said the Citizens' Security Law guarantees freedom and will have the support of a majority of Spaniards.
Street protests and strikes have became increasingly frequent in recent years following huge cuts to education and health spending aimed at shrinking Spain's public deficit to adhere to European Union demands.
But in contrast to Greece and elsewhere, where many similar protests have turned violent, Spain's have remained largely peaceful, despite unemployment of 26 percent, rising poverty, and changes in labor laws that make firing easier.
The bill, approved by the cabinet on Friday and now heading to parliament, would apply the maximum fine to unauthorized protest that turns violent inside or outside Spain's upper or lower houses.
Among other measures, protesters who cover their faces at demonstrations could be fined up to 30,000 euros while "offensive" slogans against Spain or its regions could reap a similar sanction.
"We want to guarantee a freer and more peaceful coexistence for all Spaniards ... eradicating violence," Interior Minister Jorge Fernandez Diaz told reporters.