The government has acknowledged that substantial funds meant to finance flood control have been lost through corruption.
Public anger over the issue now threatens the administration of President Ferdinand "Bongbong" Marcos Jr.
There were two large protests in the capital Manila, one organised by the Roman Catholic Church and the other by unions, students and left-wing activists.
Their complaint is the same – that money designated by the central government for flood defences was diverted into the pockets of corrupt politicians, leaving many communities dangerously exposed to this year's exceptionally heavy rainfall.
But determining who is responsible is proving harder. Marcos Jr has sacked several politicians and officials he blames for stealing flood funds.
However, one of those politicians, who is now in hiding, has accused the president himself of supervising the corruption - Marcos Jr has dismissed that as propaganda.
His own sister, Senator Imee Marcos, has now joined opposition to him, and Vice-President Sara Duterte, a bitter rival of the president, says she is ready to take over should he be forced to resign. However, she too faces different corruption allegations.
Much now depends on whether the protests continue in the coming weeks and whether any more of the president's allies desert him.
He will be mindful that two of his predecessors, including his father, were ousted by popular protest movements stirred up by corruption.