Theodore Roussopoulos was one of the prime minister's closest aides
The Greek government has come under withering attack in the press for its decision to boycott a parliamentary debate over a growing property scandal.
It follows the resignation of a second cabinet minister on Thursday.
The socialist-led opposition wants a vote on whether to set up a committee with the power to prosecute ministers suspected of wrongdoing.
But the Prime Minister, Costas Karamanlis, has ordered his MPs not to attend the debate.
Some Greek press reports suggest that if the vote had gone ahead, as many as 15 MPs from the governing New Democracy party would have abstained, leading to a defeat for the government.
In an editorial Kathimerini, a leading newspaper, condemned the government for boycotting the debate.
"We are left with the image of a ruling party that is afraid of itself," the paper said.
"In politics, battles are won by those who wage them, not by those who avoid them."
The Vatopedi all-male monastery is one of the largest in Greece
Thursday's resignation of Theodore Roussopoulos, the Minister of State and a close aide of the prime minister, has failed to reduce the pressure on the government, says BBC correspondent Malcolm Brabant in Athens.
Mr Roussopoulos stepped down following opposition accusations over the land scandal, in which state land was given to a monastery on Mount Athos, in return for much less valuable land.
The exchange, with the Vatopedi monastery, is said to have cost the state some 100m euros (£80m).
Mr Roussopoulos is a close friend of Abbot Ephraim, the chief monk at Vatopedi.
The minister said he was quitting his post so he could defend himself against a "malicious and totally groundless attack".
Last month Merchant Marine Minister Georges Voulgrakis quit over the scandal, though he too insists he has done nothing illegal.
On Wednesday parliament backed a government proposal to set up a 23-member commission to investigate the scandal.
But it does not have the power to prosecute MPs - hence the call from the opposition for a stronger committee with the power to overrule MPs' immunity.