The Greek prime minister has vowed to tackle what he has called a “deep state” he says is plaguing the country, as he sought to address a growing political crisis over a farm fraud scandal that has forced the resignation of multiple government ministers.

In a speech, aired on national TV, Kyriakos Mitsotakis attempted to limit the damage, describing the revelations as “a turning point” that had turbo-charged his commitment to rooting out entrenched corruption.

“I am striving to transform Greece into a modern European state,” he said, acknowledging its pervasive clientelistic political system. “[This] is a new starting point in the fight against the ‘deep state’.”

The leader’s intervention came days after he was compelled to reshuffle his cabinet for a second time after the scheme of fraudulent EU subsidy claims first surfaced last year.

The scandal widened last week when the European public prosecutor’s office (EPPO) announced it was investigating 20 members of Mitsotakis’s centre-right New Democracy party. Close to €300m (£260m) is alleged to have been siphoned through a state subsidy agency that has since been dissolved, over a five-year period beginning in 2017.

False claims allegedly involved banana plantations on Mount Olympus, olive groves on military air force installations and archaeological sites being cited as grazing land for livestock.

With fallout from the scandal showing no sign of abating, calls for early elections have grown. Criticism of Mitsotakis, usually a deft handler of crises, has also mounted despite his pro-business government emphasising that the fraudulent scheme began two years before he assumed power in 2019.

Georgios Samaras, an assistant professor of public policy at King’s College London, likened the leader’s address to “pure evasion and straightforward damage control”, more than nine months after he gave a similar speech revealing the state’s inadequacy in dealing with corruption.

The farm fraud scandal was of such magnitude, Samaras said, it could “yet become this government’s most serious crisis to date”.

EPPO, which has led the investigations, last week called for the parliamentary immunity of 11 New Democracy MPs to be lifted for acts of wrongdoing allegedly committed in 2021, two years after Mitsotakis assumed power. Several are prominent figures including Konstantinos Tsiaras and Ioannis Kefalogiannis, the agricultural and civil protections ministers, who both stepped down on Friday.

Intercepted phone conversations in which politicians are allegedly heard attempting to secure subsidy payments for their constituents are reportedly included in the findings of case files EPPO has presented.

“The investigation concerns alleged felonies and misdemeanours against the financial interests of the EU, namely instigation of breach of trust, computer fraud and false attestation with the intent to obtain for another an unlawful benefit,” EPPO said in a statement.

Mitsotakis on Monday called on the agency to proceed swiftly in deciding who it will prosecute, saying his MPs “have already suffered personal and political harm. They have the minimal right to defend themselves”.