He resigned on Sunday as the Greek Minister of Defense, a minor member of the Greek government coalition, protesting against the agreement closing the Macedonian-Greek name dispute and recalling six of his party ministers from the government.
Panosz Kammenos said that the Macedonian question was forced to abandon its ministerial position.
Prime Minister Alexis Cipras accepted the resignation and initiated a vote of confidence against his government.
The government of Cipras has the support of the Independent Greeks (ANEL) of the Kammenos party, with a narrow majority in the parliament, with 153 seats out of 300.
President Nicolas Vucis suggested that the vote of confidence be held on Wednesday, 16 January. Kammenos announced that his party would not vote for the government of Cipras.
The constitutional amendment that changes the name of Macedonia to Northern Macedonia has already been voted by the Macedonian parliament on Friday, but the Greek Parliament has to ratify the agreement concluded last June.
For the time being, it is not clear what the impact of the ratification process will be on the Independent Greeks leaving the government coalition with the left-wing Siriza party of Cipras. Syria has 145 mandates in the Parliament and 8 in Independent Greece.
Kammenos has always opposed the agreement with Skopje, because it feels it is unacceptable that the word Macedonia should be included in the name of the Balkan state, because it is irrevocably linked to Greek civilization and culture. The leader of the Independent Greeks has repeatedly threatened to withdraw his party from the coalition if the deal really reaches the level of parliamentary ratification.
The main opposition force, the Conservative New Democracy Party, said earlier that it would prevent the agreement from being adopted. However, the government hopes that ratification can be successful with the support of the Left and Independent Members.
Due to the Macedonian name dispute, the Greek Foreign Minister of Nykos also resigned in October last year because he felt that the head of government had not provided him with sufficient support for the Kammeno attacking the deal.
The name dispute has been between Macedonia and Greece since 1991, since Macedonia has become independent from Yugoslavia. Since the northern part of Greece, where a significant Macedonian minority lives, is called Macedonia, the Greeks believed that the Macedonians could claim territorial claims. To prevent this, they protested against a similar name choice and have hitherto hampered the Euro-Atlantic integration of the Western Balkans. Thus, the country has so far been referred to as the former Yugoslav Republic of Macedonia in international documents, but its constitution did not refer to Yugoslavia. Macedonia, with its new name, with Northern Macedonia, makes it clear that it does not claim to be in northern Greece.