Paul Leventhal

Frequently attired in his trademark bow tie, Paul Leventhal, who has died aged 69, after a protracted illness, appeared as an establishment dandy amid arms control radicals - until he opened his mouth. Compelling, sometimes abrasive, and latterly president emeritus of the Nuclear Control Institute (NCI) - which he founded 25 years ago - Leventhal was an adversary of atomic enthusiasts like no other, demanding respect from his staunchest opponents with his political insight and thoroughness of research.

Paul's work was at the heart of key security issues: nuclear terrorism, Iran's atomic aspirations, North Korea's atomic ambitions, and the future of the nuclear non-proliferation treaty, which is up for review again in Vienna next month.

During his 21 years as the NCI's president, he prepared five books, including the pathbreaking Nuclear Terrorism Taskforce final report (1985) and lectured on the threat of nuclear proliferation. He frequently visited the nuclear lion's den, the annual gathering of the Japan Atomic Industrial Forum.

The NCI website's research themes sum up his concerns: nuclear power and the spread of nuclear weapons; nuclear terrorism and how to prevent it; Saddam Hussein and the bomb; the role of India and Pakistan; plutonium and reprocessing; plutonium sea shipments; plutonium and the net; and plutonium disposal.

It was around the last of these projects that I got to know Paul best, with his involvement in the British Nuclear Fuels stakeholder dialogue. He made transatlantic visits from 2000 to examine plutonium management and security, which led to two important reports on plutonium security available at: the-environment-council.org.uk).

Born in New York, the son of a furrier, Paul was educated at Horace Mann high school and then graduated magna cum laude in government, from Pennsylvania's Franklin and Marshall College. After a master's degree in journalism from Columbia University in New York he spent a decade as an investigative reporter for the Cleveland Plain Dealer, New York Post and Newsday.

In 1969 Paul, a liberal Democrat became press secretary to the Republican New York senator, Jacob K Javits. In 1972, he served as congressional correspondent for the National Journal before returning to Capitol Hill to pursue legislative and investigative responsibilities.

One of his proudest contributions was his role in revelations of the 1977 Plumbat affair, whereby, in a high-seas heist, Israel obtained 200 tonnes of uranium for its secret nuclear weapons programme, and in the drafting of the US Nuclear Non-Proliferation Act (1978), possibly the most far-reaching legislative attempt to control the spread of nuclear weapon capability.

Paul was responsible for the investigations and legislation that resulted in another landmark law - the US Energy Reorganisation Act (1974), replacing the US Atomic Energy Commission with separate regulatory and promotional agencies. From 1976 to 1977 he was a research fellow on Harvard University's programme for science and international affairs, concentrating on nuclear weapons proliferation. He also served (1977-78) as assistant administrator for policy and planning at the US National Oceanic and Atmospheric Administration.

He was director of the senate special investigation of the Three Mile Island nuclear accident (1979-80), and prepared the "lessons learned" legislation enacted in 1980 to require preventive measures and emergency planning for future accidents. From 1979 to 1981 he was staff director of the senate nuclear regulation subcommittee. Then, in 1981, came the NCI.

For the autumn of 1991 he was a distinguished visiting fellow on Cambridge University's global security programme. He warned against the risk of terrorist attacks on nuclear plants, and rejected nuclear power as an answer to climate change. It would take 3,000 plants, he wrote in the New York Times in 2001, "a tenfold increase, to replace all coal plants; yet that increase would reduce carbon emissions by only 20%, while enormously expanding risks that materials from nuclear power plants would be applied to making weapons."

"What distinguished Paul," wrote one of his colleagues, "was his deep-seated commitment, in a city (Washington DC) full of opportunists." Paul had a hinterland too, never missing the chance to take in a new West End or Broadway play. One of his most cherished memories was of exploring the Grand Canyon with one of his sons several years ago.

Franklin and Marshall College presented him its alumni medal in 1988 and an honorary doctor of laws degree in 2001, before he proudly delivered that year's commencement address. A brown leather case, with which he was presented on departing the Congress, was an ever-present accompaniment as he criss-crossed the globe, as were his Speedo swimming trunks.

He was always fully backed by his wife, Sharon. She survives him, as do his sons Ted and Josh, two grandchildren, Griffin and Paul, and his brother Warren.

· Paul Leventhal, educator, journalist and nonproliferation expert, born February 12 1938; died April 10 2007