In 1984, after resigning from the Indian Foreign Service, Singh joined the Congress party and was elected to the 8th Lok Sabha from Bharatpur constituency in Rajasthan. In 1985, he was sworn in as a minister of state (who is a minister, but one level below a cabinet minister) and allotted the portfolios of steel, coal and mines, and agriculture. In 1986, he became minister of state for external affairs. In that capacity, he was elected President of the UN Conference on Disarmament and Development held in New York in 1987, and also led the Indian delegation to the 42nd Session of the UN General Assembly.