By Brad Haynes

SAO PAULO (Reuters) - Luiz Inacio Lula da Silva's lawyers asked on Tuesday that crusading federal judge Sergio Moro be removed from a corruption investigation involving the former president, arguing he had shown a lack of impartiality.

The filing highlighted a showdown between two of Brazil's most prominent public figures - the former president who remains a front-runner in polling for the 2018 presidential race and the judge who jailed several of Lula's closest allies.

The lawyers said a decision by Moro to publicly release Lula's wiretapped conversations in March "caused public embarrassment," leading to lawsuits in which the judge himself could eventually be held liable.

The judge's explanation of his decision before the Supreme Court also suggested that Lula had obstructed justice and concealed ownership of a country estate, Lula's lawyers told journalists in Sao Paulo, calling Moro an "accusatory judge."

The federal court in the southern city of Curitiba, where Moro has overseen a multibillion-dollar bribery probe centered on state oil company Petrobras, said in a statement that Moro would answer the accusations through the legal process.

Lula is under investigation for allegedly receiving luxury real estate and speaking engagements from engineering groups implicated in the Petrobras scandal.

Brazil's top prosecutor has also asked the Supreme Court to investigate Lula regarding allegations he benefited from the corruption scheme and obstructed efforts to investigate it.

Lula has denied wrongdoing and vowed to fight the charges.

(Reporting by Brad Haynes; Editing by Peter Cooney)