MANILA - The House of Representatives will investigate the concession contracts of Maynilad and Manila Water amid claims of irregularities that have led the government to seek a renegotiation of the agreements.

House Speaker Alan Peter Cayetano said on Facebook that congressmen will hold a hearing on the contracts on Tuesday.

Cayetano also called on the water utility firms "to show their sincerity" by waiving the P11 billion awarded to them by the Singapore court.

Manila Water was awarded P7.4-billion while Maynilad was awarded P3.4 billion.

"Also they should not just be open, but must take the lead in correcting provisions of the agreement that the President has said is bad for the country," Cayetano said.

Earlier Monday, a lawmaker claimed the water concessionaires made consumers pay for their corporate income taxes and even sports expenses.

Bagong Henerasyon Party-list Rep. Bernadette Herrera-Dy said the 1997 water concession agreements were "bursting with provisions of numerous illegalities and excessive misinterpretations all to the detriment of the Filipino people.”

President Rodrigo Duterte earlier said the government's contract with Pangilinan-owned Maynilad and Ayala-led Manila Water was unfair and that the Philippines will challenge the international arbitral court ruling ordering it to pay Manila Water.

• Solicitor General to use 'all remedies' to contest Manila Water's arbitration win

Ayala-led Manila Water Co said Wednesday it was "more than willing" to strike a "workable solution" with the Duterte government over the arbitral ruling.