Rabbi Sidney Brichto was one of British Jewry’s leading spokesmen for Progressive Judaism and most passionate supporters of Israel. He believed it the duty of diaspora Jews to demonstrate solidarity with the Jewish state and that those who blamed it for the lack of Middle East peace only aided the enemies who sought to destroy it.

Although he became the first executive director of the Union of Liberal and Progressive Synagogues (now Liberal Judaism), he grew up in a strictly Orthodox, Yiddish-speaking home in Philadelphia. Economic recession had driven his father, a kosher poultry slaughterer, to leave Jerusalem in 1930.

The early experiences of traditional Jewish celebration gave Brichto the impression of a “fun-loving” rather than guilt-inducing God. But despite his Jewish schooling, as a teenager his absorption in the classics of Western literature —The Brothers Karamazov was his favourite novel — led him to question Orthodoxy.

His break with it began one Sabbath when, transgressing the law against writing on a holy day, he underlined an admired line from Euripides in pencil — as he recalls in his engaging memoir, Ritual Slaughter: Growing up Jewish in America.

He followed his older brother Chanan to the Hebrew Union College, America’s Reform academy, combining rabbinic training with a philosophy degree at New York University. Ordained at 25, he left for London, intending to do postgraduate research in Hebrew but was invited to join the Liberal Jewish Synagogue, St John’s Wood, the UK’s Liberal flagship, as associate minister.

His energy and initiative — he established the Liberals’ evening education institute — caught the eye of the movement’s leaders, and he was appointed its professional head in 1964.

During his 25 years at the helm, he presided over the expansion of Liberal Judaism, bringing new congregations, greater democracy, a higher profile and an enhanced status for the rabbinate.

While a talmudical grandfather may have taught him that “the intellect was the essence of human life”, he displayed suitable worldliness, too. “I love Judaism,” he wrote, “but not so much as I allow other Jews to pay me less than I deserve.”

The royalties which he negotiated from the much larger American Reform movement for basing its prayer book on the Liberals’ brought valuable revenue to the British synagogue body. His fundraising and networking skills helped to secure patronage for the Liberals in other ways and also for the Oxford Centre for Hebrew and Jewish Studies, of which he was a governor.

The most radical and anglicised Anglo-Jewish denomination, Liberal Judaism had once been coloured by the anti-Zionism of some of its early 20th-century founders. Postwar, feelings had changed, and Rabbi Brichto steered the movement to closer links with Israel: rabbis pledged to give 5 per cent of their income to Israeli causes, educational trips began to the country and a youth movement was launched which later became openly Zionist in affiliation.

In 1982, disturbed by the ebbing support for Israel after the first Lebanon war, he became founding director of the Israel-Diaspora Trust, a forum for influential Jews from academia, politics, business, the law and the media, operating under Chatham House rules.

Nearly 20 years later he rebuked Liberal rabbis for having initially refused to sponsor a pro-Israel rally in Trafalgar Square (the decision was reversed). To colleagues who criticised Israel from the pulpit, he addressed the warning of a talmudic sage when Judea lay under threat from the Romans: “You wise men, be careful with your words.”

One of his boldest moves was to propose, in the lates 1980s, a joint deal on conversions with the Orthodox in an attempt to stop the damaging rift over the definition of Jewish status. The Chief Rabbi, then Lord Jakobovits, rejected his overtures, though some of his fellow Liberals would have brooked no compromise, either.

He left office as Liberal executive vice-president in 1989, moving on to work for a number of trusts, including the Joseph Levy Charitable Foundation. In later life came his most ambitious project, marrying various interests — his love of literature, attachment to the Bible and efforts for interfaith dialogue. He set about producing a modern English version of the Bible in order to reverse its fate as “the bestseller least read”.

The People’s Bible, which began appearing in volumes from 2000, cast Genesis as a verse epic, the Song of Songs as a dramatic poem. He was able to complete his translation of the New Testament — becoming the first rabbi to do so — although not the Old. Hailing Jesus as a great teacher, he was keen that the foundational texts of Christianity should be understood from a Jewish perspective. “I don’t believe we should distance ourselves from the works of Jewish boys,” he remarked.

He is survived by Cathryn, whom he married in 1971, and a daughter and three sons. His first wife, Frances, died in 1969.

Rabbi Dr Sidney Brichto, Liberal Jewish leader, was born on July 21, 1936. He died of an aortic aneurism on January 16, 2009, aged 72