Greece has repeatedly called for the return of the treasures, removed by Britain’s Lord Elgin to the then empire, known in Britain as the Elgin Marbles.
Britain is the legitimate owner of the Parthenon marbles, British Prime Minister Boris Johnson told a Greek newspaper, rebuffing Greece's permanent request for the return of the 2,500-year-old sculptures.
Since independence in 1832, Greece has repeatedly called for the repatriation of the treasures — known in Britain as the Elgin Marbles — that British diplomat Lord Elgin removed from the Parthenon temple in Athens in the early 19th century, when Greece was under Ottoman rule.
But the British Museum in London has refused to return the sculptures, roughly half of a 160-metre frieze which adorned the 5th century BC monument, saying they were acquired by Elgin under a legal contract with the Ottoman Empire and are part of everyone's "shared heritage."
In an interview with Ta Nea newspaper released on Friday, Johnson, a former student of the Classics much given to quoting Latin and Greek, reiterated that the British Museum was the legitimate owner of the marbles.
He said he understood the feelings of many Greeks about the issue but said Britain had a "firm and long-standing" position about the sculptures. "They were acquired legally by Lord Elgin, in line with the laws that were in force at that time," he said.
Greece's conservative government has stepped up pressure for a return of the marbles since it took power in 2019, a campaign it has said would be intensified by Britain's departure from the European Union.
Greece's Culture Minister Lina Mendoni last year branded Elgin a "serial thief" who used illegal tactics to take the marbles.
In 2019, Prime Minister Kyriakos Mitsotakis told Britain's Observer newspaper he would be willing to lend important artefacts to London in return for putting the marbles on display in Athens in 2021, when Greece marks the 200th anniversary of the start of its War of Independence.