ATHENS — Greece’s prime minister on Thursday defended the workings of the country’s intelligence service in the face of a wiretapping scandal, saying its operation is essential to the country’s security despite what he described as the misstep of tapping an opposition politician’s phone.

Speaking during a parliamentary debate called by the main opposition party over the wiretapping of politicians and journalists, Kyriakos Mitsotakis said that “nothing must bring into question this valuable branch of the state.”

Parliament returned early from its summer break for the debate, called by the main opposition SYRIZA party after revelations that Nikos Androulakis, head of Greece’s third-largest political party, was put under surveillance for three months last year when he was running for his PASOK party’s leadership, and that a financial journalist was also under surveillance.

Mitsotakis, who faces re-election next year, has insisted he was unaware of what he has called the legal wiretapping of Androulakis, but that he would not have approved it had he known. Greece’s National Intelligence Service reports directly to the prime minister’s office.

“When I was informed of it, I didn’t hesitate to say that it was wrong,” Mitsotakis said during his opening parliamentary speech Thursday. He has not revealed the reasons for Androulakis being under surveillance, citing national security concerns, but insisted the wiretap was legal and called on Androulakis to take the issue to Greek or European courts if he disagreed.

SYRIZA leader Alexis Tsipras slammed Mitsotakis’ handling of the issue, accusing him of criminal behavior in bugging an opposition politician’s phone without citing a reason, and calling on him to resign.

“You are legally, politically but primarily morally obliged to … state why you were surveilling the then-European MP and now head of the third largest party in Greece,” Tsipras said. “Give an answer. You are obliged to give an answer. What was this national reason? Is he an agent of foreign interests? … Is he dangerous to national security?”

The scandal has already led to the resignation of the head of EYP, Panagiotis Kontoleon, and the general secretary of the prime minister’s office, Grigoris Dimitriadis.

The three-month wiretap of Androulakis’ phone from Sept. 2021 was uncovered after Androulakis, as a European Parliament member, was informed by the European Parliament’s cybersecurity service that had had been the target of a bugging attempt by Predator spyware.

In April, Greek financial journalist Thanassis Koukakis said he had been notified by digital rights group Citizen Lab that his phone had been the target of surveillance by Predator software from July to September 2021.

The government insists it has not used Predator, but has admitted Androulakis’ phone was separately under surveillance by the intelligence service.

Androulakis filed a complaint with prosecutors at Greece’s Supreme Court on July 26 over the Predator spyware, and has demanded to know the reasons for the intelligence service surveillance.

Mitsotakis has said the government will propose changes to how EYP operates, including increasing its accountability and parliamentary supervision, and making internal changes to bolster transparency, personnel training and internal controls.