Sen. Joker Arroyo urged President Arroyo to immediately appoint a successor to Marcelo and sustain prosecution of graft cases and pursue pending cases related to the Marcos ill-gotten wealth.
"The untimely resignation of Ombudsman Sonny Marcelo is a great loss to the nation," Arroyo said.
"Sonny is a very able lawyer with a lot of integrity, the very qualities needed of an Ombudsman," he said.
Arroyo said Marcelo’s successor should also be able to institute the meaningful reform initiatives.
Opposition Sen. Aquilino Pimentel likewise said he was saddened by the resignation of Marcelo, whom he described as a trustworthy and hardworking civil servant.
"Of the officials appointed by President Arroyo, Ombudsman Marcelo may be described as among those with integrity and dedication to save the nation, not the President’s political agenda," he said.
Sen. Arroyo recognized the important role Marcelo played during the botched impeachment trial of President Joseph Estrada at the Senate in 2000.
Marcelo led a team of private lawyers that "gave tremendous support to the House prosecutors without which they could not have gone far in their job," he said.
"The chief prosecutor (now Quezon City Mayor Feliciano) Sonny Belmonte acknowledged this in his valedictory as Speaker," Arroyo added.
While Marcelo cited his deteriorating health as the reason for his resignation, Pimentel said there could be deeper reasons that forced him to quit.
"If he has resigned for health reasons, why is he staying until Nov.30? If he is suffering from poor health, maybe it should take effect immediately so that he can take a rest and undergo medical treatment," he said.
"But as I have said, Ombudsman Marcelo is very capable and I don’t think he succumbed to pressures from Malacañang on the graft cases handled by his office," the opposition senator added.
As early as last month, sources from the Integrated Bar of the Philippines (IBP) claimed Marcelo has been disgruntled over the issues pertaining to the impeachment trial of deposed president Estrada.
A member of the Estrada impeachment team claimed Marcelo "has expressed disappointment over certain decisions that concern the Estrada (plunder) case."
"In many instances, he opposed a number of concerns but the Ombudsman’s pleas were ignored," the source said.
But the source also talked highly of Marcelo, saying he was a principled man who would fight his case to the end, citing in particular his determination to see the case against the former president brought to its just conclusion.
Leonard de Vera, one of the private prosecutors who worked with Marcelo during the impeachment trial of Estrada in the Senate, described the resigned Ombudsman as a "workaholic."
He said Marcelo introduced a number of reforms at the Office of the Ombudsman.
Leaving private practice for government service, Marcelo sacrificed financial rewards when he decided to become the government’s chief graft buster after his stint in the impeachment team against Estrada, De Vera said.
De Vera expressed hopes that Marcelo will rejoin the government and be reconsidered for appointment to the Supreme Court when Chief Justice Hilario Davide retires on Dec. 20 this year.