Authorities halted construction of the plant late last year after workers were found living in cramped accommodation with "minimum comfort and hygiene conditions", the MPT said.
Some workers slept on beds without mattresses and one toilet was shared by 31 people, it said in a statement.
The MPT also alleged that construction site staff had their passports confiscated and were working under "employment contracts with illegal clauses, exhausting work hours and no weekly rest."
Prosecutors said the workers had up to 70% of their salaries withheld and faced high costs to terminate their contracts.
"Slavery-like conditions", as defined by Brazilian law, include debt bondage and work that violates human dignity.
The factory was being built in the city of Camacari in the north east of Brazil.
It was scheduled to be operational by March 2025 and was set to be BYD's first EV plant outside of Asia.
BYD, short for Build Your Dreams, is one of the world's largest EV makers. In April, it outsold Elon Musk's Tesla in Europe for the first time, according to car industry research firm Jato Dynamics.
The firm has been looking to increase is presence in Brazil, which is its largest overseas market.
It first opened a factory in São Paulo in 2015, producing chassis for electric buses.