The current holders of a valuable violin are under growing pressure to pay compensation to the heirs of its Jewish former owner, whose family music shop was seized by the Nazis.

The rare instrument, built in 1706 by the celebrated Italian luthier Giuseppe Guarneri, is worth approximately 150,000 euros, or around £133,200. But if it was repaired to its full glory, experts say it would be with at least $1 million.

It came into Felix Hildesheimer’s possession in 1938. The music shop owner took over his father’s business in 1898 and bought the rare instrument from a Stuttgart-based music dealer decades later.

Mr Hildesheimer’s shop was subjected to boycotts and later seized by the Nazis. After several unsuccessful attempts to flee the country, he committed suicide in 1939.

His wife Helene was deported to southern France a year later but survived and fled to the US in 1941. She is survived by her grandchildren Sidney Strauss and David Sand.

The violin resurfaced in 1974 when it was sold to violinist Sophie Hagemann by a luthier in Cologne. After her death in 2010, the violin went to her sole heir, the Franz Hofmann und Sophie Hagemann Stiftung, a foundation which seeks to promote young musical talent.

The foundation has said it wishes to have the violin restored and lent to students at the Nuremberg University of Music.

A mediation panel found in 2016 it was “very likely” the violin was sold under duress or seized by the Nazis.

The Limbach Commission, which handles disputes over Nazi looted art, said the foundation could keep the violin but that it should pay 100,000 euros in compensation to Mr Hildesheimer’s heirs, around £88,850.

But the foundation has not yet made a single payment, the panel revealed last week, accusing the organisation of ignoring “established standard of knowledge about living conditions” in Nazi Germany.

“For four years now, the community of heirs, whose German ancestors were subjected to severe persecution under National Socialism, has been given the impression that a political lack of will and bureaucratic hurdles stood in the way of reparation for historical injustice in Germany.

“The advisory commission considers it particularly inappropriate that the Hagemann Foundation continues to claim that its handling of the matter makes the violin an ‘instrument of reconciliation’.”

But the foundation said in a statement that “bureaucratic hurdles” had hampered its efforts to raise the sum.

It also cast doubt on the validity of the panel’s recommendation, arguing that new research suggested Mr Hildesheimer had not yet forcibly sold his shop when he purchased the violin.

“It can therefore be assumed that the violin was sold as a retail product in the music shop, because it does not appear in the list of expropriated items made by the family after the war.”

It also said it had “tried to proactively clarify the provenance of the violin and always proceeded transparently and with full awareness of the responsibility involved.”