More MPs and peers have expressed support for the repatriation of the Parthenon marbles to Greece as protesters in London mark the 13th anniversary of the opening of the Athens museum where they believe they belong.

Calls for the reunification of the antiquities, removed by Lord Elgin from the Acropolis in controversial circumstances more than 200 years ago – and regarded as vital to the nation’s cultural memory – mounted on Saturday with six UK lawmakers telling the Greek daily, Ta Nea, that restitution was the only proper thing to do. The British Museum acquired the sculptures from the diplomat in 1816.

“There could not be a better moment for the Parthenon marbles to be reunited in their Athenian home,” said Labour peer Shami Chakrabarti.

“Let us put international treasures on carefully chartered aeroplanes instead of desperate refugees,” she added, referring to the Conservative government’s controversial plan to deport asylum seekers to Rwanda.

The Scottish National Party MP, Dave Doogan, described the continued displacement of the classical carvings as a clear case of “the acquiring hand” of British exceptionalism.

“I believe the British Museum must do the right thing and return them to their rightful home in Greece. Failure to do so is insulting to Greece and her people,” he told the paper.

Addressing fears that the artworks’ repatriation could open the floodgates for other pieces to be returned to their countries of origin, another Labour peer Lord Dubs insisted that the fifth century BC Parthenon sculptures were a special case.

“We need to explain why returning the marbles would be exceptional and not set a precedent for demands for the return of hundreds of works of art all over the world,” he said. “I believe the marbles should be one entity and not in different countries, they were originally stolen from Greece but above all they represent something especially important for Greece.”

The British Museum has more than 100,000 priceless Greek artefacts in its possession although little more than six per cent of the collection is on display.

Athens has said persistently that, circumstances of ownership aside, it has no claim on any item bar the sculptures. About half of the decorative artworks that once adorned the Parthenon temple are exhibited in London. Plaster moulds of the pieces that campaigners claim were sawed and hacked from the Golden Age monument stand next to surviving originals in the Acropolis Museum.

Reinvigorating the campaign to retrieve the antiquities, the Greek prime minister, Kyriakos Mitsotakis, has increasingly spoken of the artistic, cultural and aesthetic need to put “emblematic monuments, inextricably linked with the identity of a nation”, back together so they can be viewed in their entirety as a unified whole.

With Greece placing the issue at the top of its cultural agenda, the centre-right leader made the ‘stolen’ sculptures a key talking point in his first Downing Street talks with Boris Johnson last November.

For decades the British Museum argued that the Greeks had nowhere decent enough to house artefacts that prior to their removal from the monument had been exposed to pollution and acid rain. When a magnificent state-of-the art museum was built at the foot of the Acropolis, it changed tack, saying while the sculptures could be appreciated against a backdrop of Athenian history in Athens, in London they could be viewed in the context of world history.

“The trustees firmly believe that there’s a positive advantage and public benefit in having the sculptures divided between two great museums, each telling a complementary but different story,” the Museum notes on its website.

It is not a view shared by most Britons who in successive polls have backed returning the sculptures to Greece.

On Wednesday, the British Museum’s chair, George Osborne, suggested there was a “deal to be done” that could resolve the long-running cultural row but added: “I think there’s a deal to be done where we can tell both stories in Athens and in London.”

Campaigners, who called for the return of the marbles on Saturday, said the inauguration in 2009 of an exhibition space beneath the Acropolis where research had proven that visitors spent much more “dwell time” enjoying the treasures, had robbed the British Museum of any excuse to keep the greatest work of antiquity divided. By electing to reunify the antiquities, the institution could show ethical leadership “in tune with the times”, said Paul Cartledge, emeritus professor of Greek culture at Cambridge University.

“The last vestige of an excuse for not returning the sculptures evaporated 13 years ago,” said Dame Janet Suzman who chairs the British Committee for the Reunification of the Parthenon Marbles.