Everybody who knew Rabbi Michael Rosen called him Mickey. It was a term of endearment for a very unusual spiritual leader who was more a pioneer than the conventional idea of a man of his calling.

Apart from his beard, Rosen did not look much like a conventional rabbi. He was happier in a sports shirt than a black suit. Visitors to his study were likely to find him, eyes shut, listening to Brahms or church music, rather than immersed in the study of a holy book. But that was where his pioneering came in. He believed in expressing his Judaism by acknowledging the world around him.

In short, Rosen was a very unorthodox Orthodox rabbi. That did not mean that he was not totally devoted to the faith of his fathers — and to that of his own father, in particular, who was at one time spoken of as a likely Chief Rabbi of Britain and the Commonwealth.

Mickey Rosen was above all a teacher, who dedicated most of his last years to Yakar, the organisation which he founded, first in London, and then in both Jerusalem and Tel Aviv, with the aim of fostering, as he put it, “a resonant, relevant, just and open Judaism”.

He was described as “Modern Orthodox”, but that epithet was not enough to encapsulate his ideals. Yakar, he said, was a study centre, established to foster “a Judaism based on knowledge of Torah, learning and vibrant spirituality that would at the same time be universal, nondenominational, tolerant and open to ideas and intellectual curiosity”.

There was nothing in his teaching that could offend more conventional Orthodox rabbis. But there was plenty in conventional teaching that offended him.

He might have said that he was following in the traditions adopted by his late father, Rabbi Kopul Rosen, who, at 35, was thought to be too young to be Chief Rabbi when the office became vacant in 1948. Instead, he went on to found Carmel College in Wallingford, Oxfordshire — an institution often described as Britain’s only Jewish public school. It closed in 1999.

Kolpul Rosen died in 1962 at the age of 49. Yakar is an acronym, made up of the initials of his name, Yaakov Kopul Rosen.

Mickey Rosen was the second of Kopul’s four children, three sons and a daughter. All three boys became rabbis. The eldest, Jeremy, is the head of Yakar in London. The youngest brother, David, is a former Chief Rabbi of Ireland, and rabbi of the largest congregation in South Africa, who now lives in Israel, where he has been an adviser to the government and is currently president of the International Jewish Committee for Inter-Religious Consultations and international president of the World Conference of Religions for Peace.

Mickey Rosen, like his brothers, was educated at Carmel College. He then served for a time as rabbi of the Sale Synagogue in Manchester before moving to London to found Yakar in 1979. He was awarded a PhD by London University in 1994.

His work went beyond merely putting forward his own ideas on spreading the Jewish word through Torah and Talmud. He brought to Yakar speakers who would not normally find a platform in Orthodox Jewish centres, such as Archbishop Desmond Tutu. He was also active in trying to work for better relations between Arabs and Jews and in such social endeavours as helping the poor.

His funeral in Jerusalem was attended by people of all branches of Judaism as well as those who would class themselves as non-believers — except in Rosen’s own ideals. Rabbi Yehoshua Engelman, who had succeeded Rosen as head of the London centre and is the current head of Yakar in Tel Aviv, said of his mentor that he was someone who passionately tried to show that the Jewish God is also an intelligent God.

“In Yakar he showed that religion is not primitive, that it can be worthwhile, classy, intellectual and serious and also spiritual, deep and challenging. Mickey always wanted people to challenge themselves.”

Mickey Rosen died after a fall at his Jerusalem home.

He is survived by his wife, Gila, who also taught at Yakar, and six children.

Rabbi Michael Rosen, teacher and spiritual leader, was born on January 21, 1944. He died on December 8, 2008, aged 64