Rubinstein describes Amery's deception as "possibly the most remarkable example of concealment of identity in 20th century British political history."
In his 1955 autobiography, Amery, who was assistant secretary to the British war cabinet in 1917, said his own father, Charles Frederick Amery, came from an old English family.
His mother, Elisabeth Leitner Amery, he wrote, was part of a stream of Hungarian exiles who fled first to Constantinople and then to England.
According to Rubinstein's research, Amery's mother was born to Jewish parents in 1841 and was named Elisabeth Joanna Saphir. The family lived in Pest, which later became part of Budapest and contained the city's first Jewish quarter.
Rubinstein adds that Amery changed his middle name from Moritz to Maurice in an attempt to disguise its origins.
Rubinstein, who suspects that both of Amery's sons knew of their Jewish origins, believes Leopold Amery decided to conceal his Jewishness because of fear of persecution and because it may have posed obstacles to his political ambitions.
Finally, Rubinstein asserts, Amery might have hidden his origins to avoid pressure for favors from the Jewish community.
As assistant secretary to the war cabinet, Amery not only drafted the Balfour Declaration but also was responsible for establishing the Jewish Legion, the first organized Jewish fighting force since Roman times, which became the forerunner of the Israel Defense Force.
Later, as secretary of state for dominion affairs from 1925 to 1929, he spearheaded what many regard as the most impressive period of peaceful growth in pre-state Israel.
But his most significant contribution to British politics was a powerful speech in Parliament that is thought to have played a key role in precipitating the departure of Prime Minister Neville Chamberlain in 1940 and the accession to power of Winston Churchill, who led Britain through World War II.
Ironically, one of Amery's sons, John, achieved infamy when he defected to Nazi Germany and was hanged for treason in London after World War II. The other son, Julian, succeeded his father as a member of Parliament and was a staunch supporter of Israel. He died two years ago.