The Royal Academy tried to "buy the silence" of families battling for compensation from the Russian government for priceless works of art stolen from their forebears, it can be disclosed.
The families, who claim to be the rightful owners of works in the RA's blockbuster From Russia exhibition, were each offered £5,000 by academy staff on condition that they did not launch their claims while the paintings were on display in London.
The disputed works, which include pieces by Matisse, Van Gogh and Picasso, are star attractions in the show, which explores French and Russian art from 1870 to 1925. The offer was made in December, before the Government bowed to Russian pressure and controversially changed the law to protect the works from legal challenges.
The RA confirmed last night that it had offered the payments - an admission that one art critic said left him "speechless".
André-Marc Delocque-Fourcaud and Pierre Konowaloff claim to be the lawful owners of 25 of the 120 works in From Russia. Mr Delocque-Fourcaud says that 13 of them, including The Dance by Matisse, Portrait of Dr Felix Rey by Van Gogh and Dryad by Picasso, were confiscated from his grandfather, Sergei Shchukin, by Lenin after the Russian revolution.
Mr Konowaloff, the great-grandson of the collector Ivan Morozov, insists that he is the rightful owner of another 12 paintings, including Jeanne Samary by Renoir and Mont Sainte-Victoire by Cézanne, that were also seized.
The Russian authorities threatened to cancel the RA show last year, fearing such claims might prevent the works' return to Russia. The green light was given only on January 9 after the Government had amended the law. It is understood that the Government did so after the RA had unsuccessfully tried to pay the families to ensure they would not mount claims.
Mary Anne Stevens, then the RA's acting secretary, offered the payments at a meeting in Paris, where the two men live. The RA proposed making the payment to foundations run by each man.
Mr Konowaloff said: "The Academy offered to pay us £5,000 each on condition that we would not make a claim for the works while they were on display. They wanted us to sign a document to that effect. They wanted to buy our silence."
Mr Delocque-Fourcaud also dismissed the £5,000 as unacceptable. "My lawyer told me that they were asking for a formal written guarantee not to take legal action while the exhibition was on," he said. "The grandson of the man who was robbed of billions does not accept tips."
The disclosure has provoked uproar in the arts community, which is already split over the RA's decision to profit from a show of allegedly stolen works. Brian Sewell, the art critic and broadcaster, said: "I am absolutely speechless about this. What impertinence. What meanness. If they had offered £100,000 one could see the point, but this is insulting. It's so dirty, and that is really what the Royal Academy has become now".
Charles Saumarez Smith, the chief executive of the RA, confirmed the cash offer at the meeting in Paris but declined to be drawn on the precise figure of what he called a "goodwill payment". He said: "The Royal Academy sought a great deal of legal advice about the circumstances surrounding the exhibition, including advice from the highest levels of government. It is indeed correct that there were discussions between the Royal Academy's lawyers and lawyers in France but no agreement was reached."
Both Mr Konowaloff and Mr Delocque-Fourcaud say they welcome the fact that the works are being enjoyed by audiences around the world and that they do not seek to recover the paintings.
Instead, they want the Russian authorities to compensate them for the loss, to acknowledge their family connection to the works on individual hangings and to reunite the collections.
The Sunday Telegraph understands, however, that both men asked for a share of the ticket sales. Sources close to the exhibition say the request was around £50,000.