Greek Prime Minister Alexis Tsipras is coming under increasing pressure, this time by his own lawmakers after reports emerged that some members of his government had prepared alternative plans to the tough bailout terms imposed by its international creditors.

Lawmakers are now demanding an explanation after reports that Syriza hardliners had come up with plans to raid the central bank reserves and implement a parallel tax system in preparation of the return to the drachma.

Reuters said that the plans were attributed to former energy minister Panagiotis Lafazanis and former finance minister Yanis Varoufakis, who were sacked earlier this month, noting that it is not clear how seriously the plans were considered by the government.

In an interview published on the Sunday's edition of the RealNews daily, Lafazanis said he had urged the government to tap the reserves of the Bank of Greece to allow pensions and public sector wages to be paid if Greece was forced out of the euro.

Lafazanis is the leader of a hardline faction in the ruling Syriza party that has been arguing for the return of the drachma, the news agency said.

"The main reason for that was for the Greek economy and Greek people to survive, which is the utmost duty every government has under the constitution," he said.

The centre-right New Democracy party is leading opposition party calls for the government to provide more information on these covert plans.

"The revelations that are coming out raise a major political, economic and moral issue for the government which needs in-depth examination," the conservatives said in a statement.

"Is it true that a designated team in the finance ministry had undertaken work on a backup plan? Is it true they had planned to raid the national mint and that they prepared for a parallel currency by hacking the tax registration numbers of the taxpayers?" the statement asked.

Greek referendum 5 July
Former Greek Finance Minister Yanis Varoufakis resigns after the Greek referendum. Reuters/Alkis Konstantinidis

Varoufakis while admitting that he had explored plans to create a parallel payment system while in office, said there were no plans to take Greece out of the euro.

"The context of all this is that they want to present me as a rogue finance minister, and have me indicted for treason," Varoufakis told the Daily Telegraph.

"It is all part of an attempt to annul the first five months of this government and put it in the dustbin of history. It totally distorts my purpose of wanting parallel liquidity," Varoufakis said.

Deputy Finance Minister Dimitris Mardas has denied that the government had ever discussed plans to take Greece out of the euro, telling Skai television: "I have repeatedly said that such discussions have never taken place at a government policy level."

Tsipras struggling to keep party intact

Ekathimerini reports that Tsipras is now struggling to keep his party intact, especially now that his party's 149 MPs are deeply split over the terms of the international bailout that was agreed to by Tsipras.

Tsipras had apparently indicated that a party congress should be held in September to refocus Syriza and the news agency does not rule out early elections in either September, October or November, given the "inevitable" upheaval within the party.

State Minister Nikos Pappas has said on Saturday that the country could not continue indefinitely with a minority government, referring to the mass defections by Syriza MPs in the recent parliamentary votes.

A meeting of the Syriza's political secretariat is due to take place on Monday, Ekathimerini said.