President Garcia has seen his approval rating fall
Thousands of people have taken to the streets in several Peruvian cities to protest against the rising cost of living and low wages.
The demonstrations, planned weeks ago, took place just days after a scandal allegedly involving officials taking bribes for oil concessions emerged.
Voters say corruption is one of their main concerns about President Alan Garcia's government.
Mr Garcia, who took office in 2006, has seen his popularity fall sharply.
The demonstrations, organised by the biggest trade union, were called to demand a change in the government's free market policies, which opponents say have failed to improve living standards for many Peruvians.
But just days after a scandal allegedly involving kickbacks in return for oil contracts emerged, the protesters also took up the theme of corruption.
In the capital, Lima, thousands of workers, including teachers, builders and doctors marched on Congress on Tuesday, calling for the cabinet to step down.
The governing party, Apra, is stealing while the people are struggling, they chanted.
Trouble broke out when a group that did not appear to be linked to the main protest began throwing stones at the police, who responded with tear gas.
The demonstrations could not have come at a worse time for President Garcia, with opinion polls putting his approval rating at its lowest level since he took office, says the BBC's Dan Collyns in Lima.
Mr Garcia ordered an investigation after the alleged scandal surfaced on Sunday, and insisted that the government must be purged of corruption.
But the damage control may be too late to save the government's reputation, says our correspondent.
On Sunday, a TV station broadcast a tape of a top state oil official and a lobbyist apparently agreeing to favour an oil company in a round of auctions for oil concessions.
The taped conversation was allegedly between Alberto Quimper, a executive with the state energy agency, Perupetro, and a prominent lobbyist Romulo Leon.
The company, Discover Petroleum of Norway, has said it made payments to Mr Leon and to a law company employing Mr Quimper, but it denied paying any bribes, Reuters reported.
"The application process (was) completely open and transparent, and could not possibly have been influenced by any bribes," Discover said in a statement.
Peru's energy sector has pushed hard to attract billions of dollars in foreign investment in the country's huge mining industry and its fast-growing oil and gas sector.