Story highlights Brazil approves a constitutional amendment that caps public spending

Protesters take to the streets in 15 cities over the amendment

(CNN) Fierce protests erupted in 15 Brazilian cities Tuesday as the country's Senate approved a controversial 20-year austerity plan.

Known as PEC 55, the constitutional amendment imposes a cap on public spending that will limit federal investment in social programs for the next 20 years.

Brazil's Senate approved the spending bill 53 to 16, and it is expected to become law Thursday.

Photos: Brazilians protest austerity plan Protesters throw a flare towards the Sao Paulo Industry Federation building in Sao Paolo, Brazil, on Wednesday, December 14. Protests erupted across 15 cities in Brazil as lawmakers voted to pass constitutional amendment PEC 55, which will limit public spending over a 20 year period. Hide Caption 1 of 12 Photos: Brazilians protest austerity plan Demonstrators face-off with police in the city of Brasilia on Tuesday, December 13. Hide Caption 2 of 12 Photos: Brazilians protest austerity plan A protester fires a slingshot at police during a demonstration in Brasilia on December 13. Hide Caption 3 of 12 Photos: Brazilians protest austerity plan A demonstrator holds a sign that reads, "peace, love, and unity," in the midst of a clash between protesters and police outside the National Congress in Brasilia on December 13. Hide Caption 4 of 12 Photos: Brazilians protest austerity plan Riot police fire tear gas grenades at protesters in Brasilia on December 13. Hide Caption 5 of 12 Photos: Brazilians protest austerity plan A protester gestures in front of the National Congress in Brasilia on December 13. Hide Caption 6 of 12 Photos: Brazilians protest austerity plan A fight breaks out between demonstrators and police in Brasilia on December 13. Hide Caption 7 of 12 Photos: Brazilians protest austerity plan A police officer is seen with an injury during clashes with protesters in Brasilia on December 13. Hide Caption 8 of 12 Photos: Brazilians protest austerity plan A bus blazes after being set on fire by protesters in Brasilia. Hide Caption 9 of 12 Photos: Brazilians protest austerity plan A police officer wears a white flower on his bulletproof vest while participating in a public servants' protest against the austerity measures in front of the State Assembly in Rio de Janeiro on Monday, December 12, as lawmakers began the voting measures. Hide Caption 10 of 12 Photos: Brazilians protest austerity plan A demonstrator sits wrapped in a Brazilian flag outside the state legislature in Rio de Janeiro on December 13, where police, firefighters, and teachers gathered for the rally. Hide Caption 11 of 12 Photos: Brazilians protest austerity plan An indigenous man sings during a rally in Rio de Janeiro on December 12. Hide Caption 12 of 12

Brazilian President Michael Temer -- who assumed office in late August -- praised the move, referring to the bill as the "first amendment aimed at getting the country out of recession."

The government hopes that the spending cap, combined with a proposed pension reform, will lure investors back to Brazil, bringing an end to the worst recession in decades.

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