The son of a German-Jewish doctor who lived in the UK is fighting the Claims Conference, the Holocaust restitution agency, over a property he says belongs to his family.

Heinrich Ruhemann, 80, from Darmstadt, Germany, says the apartment block in East Berlin was bought by his father, Ernst, in 1935.

But the German government has refused to recognise his claim and he has been ordered to transfer the building, worth around £900,000, to the conference under restitution laws.

“We are not going to lose it without trying to defend ourselves,” Mr Ruhemann said. “I am not giving this up.”

His father, who grew up Jewish in Germany but became Christian, bought the building from a Jewish family who wanted to leave the country. He registered it in the name of his non-Jewish wife, Hildegard.

Ernst Ruhemann left Germany in 1939, seeking refuge for his family, and came to London on the eve of the Second World War. Heinrich survived the war in Germany with his mother and sister, although “in 1943, I was told to leave school and I couldn’t get a job or apprenticeship, being considered as a half-Jew”.

After the war, his mother and sister, Ursula Cox, who now lives in Nuneaton, emigrated to the UK to rejoin their father, who died in 1952. When Hildegard died in 1991, she left the German property to her son.

The disputed property at 22 Korsoerer Strasse, Berlin, was taken into administration by the Communist authorities, but after the reunification of Germany some 40 years later, the family reclaimed it. Mr Ruhemann said he had since invested £65,000 in repairs.

He now believes he has fallen foul of the German government’s Holocaust restitution policy. According to the law, the heirs of Jews who sold property in East Germany under duress could file a claim on it until the end of 1992, after which if there were no recognised claims, ownership could be asserted by the Claims Conference.

He said that he had made an offer of £635,00 to settle with the Claims Conference last year, but the organisation had rejected it and now wants him to pay around £90,000 earned in rent from tenants since 1994.

The Claims Conference said it had insufficient time to respond in detail.