My father, Ian Semple, who has died aged 82, was an outstanding member of the Bahá'í faith – a world religion that promotes the unity of humankind – and served for 42 years on its international governing council, the Universal House of Justice.

Ian had a serene, wise and balanced personality, and adhered scrupulously to moral principles regardless of what it might cost him personally. He possessed an inquiring mind and took great delight in conversing on almost any subject. His children, family, friends and co-workers invariably felt they could approach him with any problem and knew that he was always ready to listen, no matter how busy he might be. Ian's many achievements never affected his sense of humility.

Born in Barnet, north London, Ian served in the army from 1947 until 1949 and earned a commission in the Royal Corps of Signals. He then studied German and French at Pembroke College, Oxford, before going on to train as an accountant.

Ian became a Bahá'í in 1950 – a defining moment in his life. Thereafter, he dedicated himself to promoting its teachings, including the oneness of religion, the equality of men and women, and the need to abolish all forms of prejudice. Abandoning accountancy, Ian served on various national and international Bahá'í administrative bodies, culminating in his election to the first Universal House of Justice in 1963. Ian was successively re-elected every five years, until his retirement in 2005. He had been one of only 500 Bahá'ís in the UK in 1950; by 2005 the British community had become more than 6,000 strong.

After retirement, Ian moved to Switzerland, where many members of his family live. He is survived by his wife Louise, whom he married in 1963, two sons, me and Nick, and a daughter, Jenny.