Brazil's deputy prosecutor for elections, Humberto Jacques de Medeiros, on Monday called on the Superior Electoral Court (TSE) to reject ex-President Luiz Inacio Lula da Silva as a candidate in October elections.

The motion comes after Brazil's Workers' Party registered Lula as its candidate on Wednesday, despite his being behind bars, serving a 12-year prison sentence for corruption.

His request to the court cites Brazil's Clean Record Act, which bars those convicted of a crime from running for elected office.

"Indeed, the candidate is ineligible," De Medeiros argued.

The decision ultimately rests with the TSE, the nation's top electoral body.

Also Monday, a new poll showed Lula maintains a firm lead over the other 12 proposed candidates.

The polling firm MDA Institute survey shows Lula leads with 37 percent of voters, and would easily win a runoff.

Last week, the United Nations Human Rights Commission called on the Brazilian government to grant Lula the right to exercise his political rights from prison, including access to the press and members of his party.

Lula's defense team has argued that the commission's decision carries legal weight in the country and its findings should be presented before the TSE in asking that his candidacy be validated.