He was born in Hadali, Punjab (which now lies in Pakistan), to a Sikh family. His father, Sir Sobha Singh, was a prominent builder in Lutyens' Delhi.

He was educated at Government College, Lahore, St. Stephen's College in Delhi and King's College, London, before reading for the Bar at the Inner Temple.

In August 1947, days before the partition of India and Pakistan, Singh, then a lawyer practicing in the High Court in Lahore, drove to his family's summer cottage at Kasauli in the foothills of the Himalayas. Continuing on to Delhi along of vacant road, he came upon a Jeep of armed Sikhs who boasted that they had just massacred a village of Muslims. Such experiences were to be powerfully distilled in Singh's 1956 novel Train to Pakistan. (The 2006 edition of Train to Pakistan, published by Roli Books in New Delhi, also contains 66 photographs by Margaret Bourke-White that capture the partition's violent aftermath.)

Singh has edited Yojana, an Indian government journal; The Illustrated Weekly of India, a newsweekly; and two major Indian newspapers, The National Herald and the Hindustan Times. During his tenure, The Illustrated Weekly became India's pre-eminent newsweekly. After Singh's departure, it suffered a huge drop in readership.

From 1980 through 1986, Singh was a member of Rajya Sabha, the upper house of the Indian parliament. He was awarded the Padma Bhushan in 1974 for service to his country. In 1984, he returned the award in protest against the siege of the Golden Temple by the Indian Army. In 2007, the Indian government awarded Singh the Padma Vibhushan.

Singh is said to wake up at 4 am each day and write his columns by hand. His works range from political commentary and contemporary satire to outstanding translations of Sikh religious texts and Urdu poetry. Despite the name, his column "With Malice Towards One and All" regularly contains secular exhortations and messages of peace. In addition, he is one of the last remaining writers to have personally known most of the stalwart writers and poets of Urdu and Punjabi languages, and profiles his recently deceased contemporaries in his column. One of the most striking aspects of his weekly writings is his outright honesty; he will openly admit to his weaknesses and mistakes, along with an acceptance of his declining health and physical abilities in more recent times.

As a public figure, Singh has been accused of favoring the ruling Congress party, especially during the reign of Indira Gandhi. He is better viewed as an establishment liberal. Singh's faith in the Indian political system has been shaken by events such as anti-Sikh riots that followed Indira Gandhi's assassination, in which major Congress politicians were alleged to be involved. But he has remained resolutely positive on the promise of Indian democracy and worked via Citizen's Justice Committee floated by H. S. Phoolka who is a senior advocate of Delhi High Court.

He has a son named Rahul Singh and a daughter. He is the paternal uncle of actress Amrita Singh.

He is an atheist. In his article on hindustantimes he wrote, "I don’t believe in God, satan, angels, devils, heaven or hell."

Television Documentary: Third World...Free Press (also presenter; Third Eye series), 1982 (UK).