The five-member team working with Varoufakis could face charges of being part of a criminal organization.

Greek Supreme Court Prosecutor Efterpi Koutzamani issued a new lawsuit against the former finance minister Yanis Varoufakis for his involvement in a five-membered group of close associates eyeing a plan for Greece’s exit from the eurozone, known as Plan B.

Varoufakis is immune from criminal prosecution because of his position as an MP, this protection could be overturned by the Greek parliament in a ballot when it reviews the allegations. With Greek banks operating under capital controls and the worldwide standing of Athens damaged after months of acrimonious talks with creditors, largely overseen by Varoufakis, calls are also growing for the academic-turned-politician to be tried for high treason.

The former minister confirmed on Monday that he had made secret preparations to hack into citizens’ tax codes to create a parallel payment system after the disclosure provoked shock and disbelief in Greece, Reuters reported.

Mr Varoufakis, who stepped down as finance ministerб this month, has played down the initiative as a contingency plan that was never implemented.

The revelations involving Varoufakis overshadowed the start of work in Athens between the Greek government and its worldwide creditors on launching a third bailout programme for Greece by mid-August.

The furore piled new pressure on a premier struggling to contain a leftist party revolt.

The Official Monetary and Financial Institution Forum, who hosted the call, released a recording of it, thus implicating Varoufakis.

Mr Varoufakis’s team included respected US economist James K Galbraith, and touted the use of smartphone apps to allow the state to continue making its domestic obligations to suppliers and collecting tax revenues.

At one point, the moderator cautioned Varoufakis that other people were listening to the teleconferenceб but would not repeat its contents. Government insiders have refused to be drawn on the former finance minister’s claims. “And even if theyб do I will deny I said it”.

He told investors that he secretly worked with a computer expert from Columbia University, who was also his “childhood friend”, to hack the private identification numbers of state employees, under the instruction of Prime Minister Alexis Tsipras.

He has since said that the plans were carried out within “the laws of the land, and at keeping the country in the eurozone“.