ATHENS, Greece — Taking a huge political gamble, Greece’s prime minister announced Monday that his debt-strapped country will hold a referendum on the new European debt deal reached last week — the first such vote in 37 years.

Prime Minister George Papandreou appeared to take many lawmakers by surprise by saying that a hard-bargained agreement that took months for Europe’s leaders to hammer out will be put to a public ballot.

He gave no date or other details on the proposed referendum, which would be the first in Greece since 1974, when the monarchy was abolished by a landslide vote months after the collapse of a military dictatorship.

“This will be the referendum: The citizen will be called upon to say a big ‘yes’ or a big ‘no’ to the new loan arrangement,” Papandreou told members of parliament. “This is a supreme act of democracy and of patriotism for the people to make their own decision. ... We have a duty to promote the role and the responsibility of the citizen.”

The move allows Socialist lawmakers — who have been vilified by an increasingly hostile public during months of strikes, sit-ins and violent protests over rounds of austerity measures — to pass the responsibility for the country’s fate to the Greek people themselves.

Finance Minister Evangelos Venizelos, a constitutional law professor, said the referendum was called after opposition parties repeatedly failed to side with the government in negotiations between Greece and other eurozone members.

“Greece is living through a drama, from which it must be released by asking the people to express its will,” Venizelos told parliament.