BRASILIA, Sept. 10 (Xinhua) -- Brazil's left-leaning Workers' Party (PT) on Monday appealed to the Supreme Federal Court (STF) for more time to designate an alternative candidate to compete in the upcoming presidential elections.

The appeal was filed a day before the deadline to name a substitute for former president Luiz Inacio Lula da Silva, whose candidacy was disqualified on Aug. 31 due to his conviction on corruption charges.

Lula's lawyers had filed a similar appeal to the Superior Electoral Court, but the president of the top election body denied the motion earlier in the day.

Lula's running mate, former mayor of Sao Paulo and ex-minister of education Fernando Haddad, is his likely replacement, though prosecutors recently accused him of campaign finance irregularities.

Lula is serving a 12-year jail sentence, but has been banking on a series of appeals to absolve him so he can run again.

According to polls, the two-time president has consistently led the field of 13 candidates by a wide margin, despite his legal troubles. He has steadfastly denied any wrongdoing, alleging the charges were politically motivated to derail his run for reelection.

His lawyers also petitioned the STF to overrule the electoral court's decision to disqualify his candidacy based on Brazil's Clean Record Act, which bars anyone with a criminal conviction from seeking elected office.

The PT wants the deadline extended until Sept. 17, hoping for a breakthrough in Lula's ongoing appeals process.