In this file photo dated Jan 9, 2023, visitors view the Parthenon Marbles, also known as the Elgin Marbles, at the British Museum in London. (PHOTO / AFP)

LONDON/ATHENS - A dispute between Britain and Greece over the ownership of the Parthenon Sculptures, known as the Elgin marbles, escalated on Tuesday, with both sides blaming the other for the cancellation of a planned meeting between their two leaders.

Prime Minister Rishi Sunak cancelled Tuesday's meeting with his Greek counterpart Kyriakos Mitsotakis after his office said the two sides had previously agreed that it should not be used as a public platform "to relitigate long, long settled matters".

"It's simply the case that if assurances are given and they're not adhered to, that there are consequences for that," Sunak's spokesman told reporters.

Greek government spokesman Pavlos Marinakis said the cancellation was unprecedented and disrespectful but added that Athens did not want to let the row with Prime Minister Rishi Sunak spoil normally good relations between the countries

A senior Greek government official speaking on condition of anonymity dismissed the statement as "inaccurate".

Greece has repeatedly called on the British Museum to permanently return the 2,500-year-old sculptures that British diplomat Lord Elgin removed from the Parthenon temple in 1806, during a period when Greece was under Ottoman Turkish rule.

About half of the 160-meter frieze that adorned the temple is in London, while another 50 meters are in the Acropolis museum in Athens, whose top floor layout mimics the Parthenon.

ALSO READ: Sunak cancels Greek PM meeting in Parthenon sculptures row

Appearing on the BBC over the weekend, Mitsotakis compared the separation of the carvings to cutting the Mona Lisa in half, a characterization rejected by the British government.

"The PM did not say something new. Greece's positions on the Parthenon sculptures issue are known," said Aristotelia Peloni, an advisor to Mitsotakis on international policy. "Disagreeing on certain issues does not mean that we cannot talk."

In this file photo dated Jan 9, 2023, visitors view the Parthenon Marbles, also known as the Elgin Marbles, at the British Museum in London. (PHOTO / AFP)

Both Britain and Greece said that the dispute jeopardized the opportunity to discuss global issues. The two leaders would have also discussed a UK-Greece migration action plan.

Greek government spokesman Pavlos Marinakis said the cancellation was unprecedented and disrespectful but added that Athens did not want to let the row with Sunak spoil normally good relations between the countries.

ALSO READ: Greece PM laments lack of progress with UK on Parthenon Sculptures

In this file photo dated June 8, 2021, visitors walk down the new cement walkway nearby the Parthenon temple on the Acropolis hill in Athens, Greece. (PHOTO / XINHUA)

Plot twist

Later on Tuesday, British Foreign Secretary David Cameron and his Greek counterpart George Gerapetritis met on the sidelines of a NATO ministers' meeting in Brussels, Greek diplomats said.

"The two ministers agreed that there is need for cooperation to safeguard the Greece-UK bilateral relations and tackle the common challenges," one of the diplomats said, adding that the Greek minister noted the disagreement of principle on the Parthenon sculptures issue.

Sunak's decision to cancel the meeting was also criticized by some British opposition parties and a campaign group backed by British politicians from different parties who want to resolve the issue

Sunak's decision to cancel the meeting was also criticized by some British opposition parties and a campaign group backed by British politicians from different parties who want to resolve the issue.

Greece does not recognize the British Museum as owner of the sculptures.

ALSO READ: Austria says talks underway on returning Parthenon marbles to Greece

The group, the Parthenon Project, has proposed a deal that would see the sculptures reunified in Athens - without Britain and Greece needing to agree on who owns them.

Ed Vaizey, a former Conservative culture minister who advises the group, said that Sunak's action was a "plot twist" given Britain's previous stance that resolving the issue was a matter for the British Museum itself.

Britain's Prime Minister Rishi Sunak delivers a speech at a college in north London, Nov 20, 2023. (PHOTO / AP)

"The prime minister has put himself at the front and center of row that he didn't really need to put himself at the front and center of," Vaizey told Sky News. "I don't think the prime minister needed really to intervene in this way and it hasn't particularly helped our relationships with Greece."

Britain's government has long cited a law that prevents the British Museum from disposing of items in its collection in most circumstances.

READ MORE: Greek PM dashes hopes of swift return of Parthenon marbles

Asked if the government was concerned that other countries might also seek restitution of items if a deal was reached to return the marbles, Sunak's spokesperson said: "We do think it is potentially a slippery slope, and that's not something that we would support."