"Don't follow any imbecile decisions by the president of the republic or the health minister: Get vaccinated," Lula, now 75, told reporters, in reference to Bolsonaro's vaccine skepticism and defiance of medical advice.
The coronavirus pandemic has killed more than 266,000 people in Brazil, making it the second-hardest-hit nation, after the United States.
"This country has no government, this country doesn't take care of the economy, of job creation, wages, health care, the environment, education, young people," Lula said, in a press conference at the metalworkers' union he once headed in Sao Bernardo do Campo, outside Sao Paulo.
Bolsonaro responded to Lula's attack on Wednesday, saying the leftist leader was launching his 2022 presidential campaign election by criticizing the president.
"Lula is already in campaign and he has nothing good to show, his campaign is based on lies and disinformation. He is rambling, he does not know what he is talking about," the president said in an interview with CNN Brazil.
Lula makes political return
The comments, made just days after a key victory in court, marked Lula's return to politics.
On Monday, a Supreme Court judge annulled the former president's criminal convictions and reinstated his right to run for office. The decision paves the way for Lula to run against Bolsonaro in 2022. On Wednesday, Lula called himself the victim of the "biggest judicial lie in 500 years." He dismissed the corruption charges he had been convicted of as designed to keep him from winning the 2018 presidential race, which saw Bolsonaro take power.
Lula said he planned to "fight tirelessly" for Brazil, and that he wanted to resume touring the country once he receives the COVID-19 jab next week.
The leftist leader is a former metalworker and union leader who saw Brazil through an economic boom from 2003 to 2010.
"Brazil doesn't deserve this," he said on Wednesday.
'No time to think about 2022'
Lula didn't offer any information about whether he would run next year. "My head doesn't have time to think about a 2022 candidacy now," he told reporters.
The former president was implicated in a scheme that saw politicians and executives receive billions of dollars from the state oil company, Petrobras.
Lula spent 18 months in prison before being released in 2019. He is still seen as a heroic figure by leftists, who believe that Lula was the victim of a conspiracy. Bolsonaro ultimately made the lead judge in the Lula probe his justice minister. Supporters of the former president point to hacked phone messages as evidence of a setup.
Bolsonaro ahead of Lula in possible 2022 matchup, survey says
A poll released by the CNN Brasil news channel on Wednesday found Bolsonaro ahead of Lula if the two leaders square off in 2022. The survey shows Bolsonaro 10 points ahead of Lula in the first round, 31% to 21%, with former Justice Minister Sergio Moro in third place at 10% support.
If no candidate receives more than 50% in the first round, the top two candidates face each other in a runoff. In this scenario, the survey shows Bolsonaro with 43% of the vote, with Lula garnering 39% support.
The CNN survey has a 3-point margin of error, with data being collected from 1200 Brazilians across the country.
lc, wd/dj (AFP, Reuters, AP)