Greek Prime Minister Kyriakos Mitsotakis apologised to the leader of the country's opposition Socialist party for not knowing that he had been wiretapped by Greece's intelligence service in 2021, adding he would never have allowed it.
The case has shocked Greeks and sparked political uproar.
The head of the intelligence service EYP, Panagiotis Kontoleon, resigned on Friday following allegations made by Socialist leader Nikos Androulakis and a journalist that they had been wiretapped. read more
In a preview of Sunday's To Vima newspaper, Mitsotakis was quoted as saying: "I wasn't aware, I would have never allowed it. I owe Mr. Androulakis an apology for the mistake made."
"It was a serious and unforgivable mistake," he added.
The conservative premier is expected to make a public address over the case on Monday, the semi-state Athens News Agency reported on Saturday.
Androulakis, who was elected PASOK leader in December 2021, said on Friday evening that he had learned EYP listened to his conversations in late 2021. He did not disclose the source of the information.
The government said it had been made aware of Androulakis' surveillance, which it said was lawful as it had been approved by a prosecutor, and had sought to inform him, "but Androulakis chose not to respond."
Androulakis has called on Greece's parliament to set up an investigative committee to look into the case. The government has said that it would back the request, if submitted officially.
On July 26, Androulakis also filed a complaint with the country's top court prosecutors over an attempted bugging of his mobile phone with surveillance software, in what appeared to be a separate case.
The complaint comes as the European Union is beginning to follow the United States in taking a harder look at spyware merchants and the use of powerful surveillance software.
Last week, two lawmakers who spoke to Reuters on condition of anonymity said that Kontoleon had admitted during a parliamentary committee on July 29 that his service had spied on Thanasis Koukakis, a financial journalist who works for CNN Greece. read more