Greece has condemned the British Museum's decision to reject a UNESCO offer to help resolve a decades-old dispute over returning ancient Parthenon sculptures to Athens.
The sculptures are part of the collection popularly known as the Elgin Marbles which were acquired by Lord Elgin in the early 1800s when he was ambassador to the Ottoman court.
The British parliament purchased the art treasures in 1816 and gave them to the museum.
For the past 30 years, Athens has been demanding the return of the sculptures which had decorated the Parthenon temple on the Acropolis in Athens from ancient times.
"We deplore the categorical refusal by the British of UNESCO's invitation to launch a mediation process over the Parthenon sculptures housed in the British Museum," Greek culture minister Nikos Xydakis said.
"The British negativism is overwhelming, along with its lack of respect for the role of mediators."
We believe that the more constructive way forward, on which we have already embarked, is to collaborate directly with other museums and cultural institutions
Sir Richard Lambert
The UN cultural agency had offered to mediate between Greece and Britain over the ancient artworks during a meeting in October 2014.
But Sir Richard Lambert, the director of the British Museum, said in a letter to Athens this week that the trustees "decided respectfully to decline this request".
He said UNESCO's role was to pursue and safeguard endangered cultural heritage and that "the surviving Parthenon sculptures, carefully preserved in a number of European museums, clearly do not fall into this category".
"We believe that the more constructive way forward, on which we have already embarked, is to collaborate directly with other museums and cultural institutions, not just in Greece but across the world."
Sir Richard said the British Museum wanted to continue exploring collaborative ventures directly with Greek institutions - "not on a government-to-government basis".
For his part, the Greek minister criticised Britain for viewing the dispute as just an issue between museums and not between states.
"We call on Great Britain to reconsider its position," Mr Xydakis said.