Senator Antonio Trillanes, one of only a few politicians who regularly challenge the popular president, released copies of what he said were bank statements from 2006 to 2015, totalling 2.4 billion pesos (HK$372.8 million) in numerous accounts, that he said belonged to Duterte and which he had failed to declare before his election last May.
According to the copies, some of the accounts were joint accounts that Duterte held with people close to him, including relatives.
"If my allegations are proven wrong, I will immediately resign as senator," Trillanes, a former navy lieutenant who led a failed coup in 2003, told a news conference.
In a radio interview, Duterte's legal counsel, Salvador Panelo, dismissed the allegations as "old issues" and said Trillanes was "only looking for free publicity."
Duterte's spokesman, Ernesto Abella, said the president may release the history of his bank transactions, if necessary, but not in response to the senator's allegations.