Brazil's President Luiz Inacio Lula da Silva has vowed to continue in office despite corruption allegations levelled against his party.
Lula insisted he still has "moral authority" to govern Brazil
Speaking in central Brazil, Lula denounced his accusers, saying: "They don't know who they're dealing with."
He told an audience of farmers that he would welcome any investigation.
Lula's Workers Party has been accused of paying bribes to allies in Brazil's Congress. Last week his chief of staff resigned over the accusations.
"Corruption is not a game," an angry Lula told farmers in the central Brazilian state of Goias.
"You can't stain the name of people. You can't strip them bare in front of society, and later prove nothing."
The corruption allegations have grown into the worst scandal during former union leader Lula's period in power in Brazil.
He won power in 2002 pledging to crack down on endemic corruption in Brazil.
But despite repeatedly stressing his humble origins, Lula's popularity has waned in the face of slow economic growth and gathering corruption allegations.
Recent polls have rated his public support at just 39%.
Lula's chief of staff, Jose Dirceu, resigned last week despite denying involvement in the alleged bribery ring.
Correspondents say he was trying to shield Lula from further allegations.
Roberto Jefferson, a member of the Labour party, a government ally, has accused the Workers' Party of paying bribes to win political support.
A coalition of 40 social groups, including the leftist landless movement, have pledged to support Lula and root out corruption, Reuters reports.