The reforms would force Brazilians to work more years before being eligible for full retirement benefits.
About 71 percent of people in Brazil oppose the pension reform introduced by senate-imposed President Michel Temer, according to the latest poll issued Monday by the daily Folha de Sao Paulo.
Only 23 percent said they supported the reform, with an estimated 2 percent margin of error.
The pension reform, a key measure of Temer's austerity plan, set a minimum age of retirement at 65 years. It also plans to reduce death pension benefits, while raising social security contributions by civil servants.
The survey also found that 64 percent believe that only the business sector will benefit from the labor reform, approved in the lower house last week.
Temer's scandal-plagued government is also immensely unpopular, with a staggering disapproval rating of 87 percent, according to the latest Ipsos poll.
Chanting slogans like “No to the reforms, No to police violence: resistance!” workers, social movements and labor unions demonstrated in the main cities of the country for International Workers Day, denouncing the violent repression on Friday in Rio de Janeiro by the military police.
Just days before, an estimated 35 millions of Brazilian workers took their opposition to the reforms to the streets in two-days general strike started before the weekend, according to the country's main labor union CUT.
The Bill 6787 would undermine workers’ rights by eliminating payment for their commute from their contracts, reducing compensation for employer abuse, and most importantly, allowing employers to reduce workers’ salaries while increasing their work hours.
The bill, which also proposes to end mandatory union dues, must still be approved by the Senate. It was approved by Brazil's lower house by 296 votes to 177.
Temer is also proposing a 20-year freeze on public spending and cuts to pension protections.