Brazil's Supreme Court has acquitted the head of the once-dominant leftist Workers' Party of charges of corruption and money laundering.

Gleisi Hoffmann, a senator, is the latest in a long string of high-ranking politicians, including many from the Workers' Party, caught up in Brazil's sprawling "Car Wash" corruption probe.

Her husband Paulo Bernardo, a former planning and communications minister, stood trial at the Supreme Court as part of the same case against Hoffmann. He, too, was found not guilty.

Prosecutors accused the couple of receiving a million reais in 2010, or $568,000 at the time, embezzled from state oil company Petrobras. The money from the company was allegedly used in a campaign slush fund.

Investigators have uncovered a huge web of corruption centered on Petrobras, with the company handing out inflated contracts to Brazilian companies in exchange for bribes, many of which went into politicians' pockets.

Hoffmann's acquittal was a sweet win for the battered party which led Brazil between 2003 and 2016 under presidents Luiz Inacio Lula da Silva and Dilma Rousseff.

Lula, who founded the Workers' Party, was imprisoned in April after being convicted of corruption. Rousseff is out of politics, having been impeached and removed from office in 2016.

Hoffmann, who took over the party leadership in June 2017, said in a statement before the verdict that she had been "unjustly accused, with no evidence."