Paul Leventhal, journalist, author and president of the Nuclear Control Institute in Washington, was best known for his staunch opposition to the civil use of nuclear power to generate electricity.

His main objection was that an inevitable by-product of ordinary uranium-fuelled nuclear reactors is plutonium. This plutonium can be chemically removed from spent reactor fuel in a reprocessing plant and used to produce nuclear weapons. Leventhal was also concerned about the safety of nuclear power plants and the threat of another Chernobyl-like nuclear disaster.

In the last few years of his life he concentrated on the increasing risk of nuclear terrorism. He gave warning that, as the global stocks of plutonium separated from spent nuclear fuel increase, the danger that terrorists will get hold of plutonium and fabricate and detonate a crude nuclear weapon also increases.

He worried much about the future of the Non-Proliferation Treaty (NPT). Iran’s nuclear ambitions and North Korea’s nuclear weapon programme are, he argued, considerable threats to the already fragile treaty. He had particularly strong views about Iran. He was convinced that Iran has a clandestine nuclear weapons programme and argued that harsh steps should be taken to stop it getting nuclear weapons, perhaps even by military strikes.

The emergence of any new nuclear-armed powers would, Leventhal believed, probably destroy the NPT, the main international instrument to prevent the further spread of nuclear weapons to countries that do not now have them. The more nuclear weapon powers there are, the more likely it is that nuclear weapons will be used, sooner or later.

Paul Lincoln Leventhal was born in New York in 1938. He was educated at the Franklin and Marshall College, Lancas-ter, Pennsylvania, graduating in 1959. In 1960 he received a master’s degree from the Columbia School of Journalism.

He then worked as a political and investigative journalist for The Plain Dealer in Cleveland, the New York Post and News-day. In 1969 he moved to Washington to become press secretary to Jacob K. Javits, a New York Republican senator. From 1972 to 1976 he worked as special counsel to the US Senate Government Operations Committee. Between 1976 and 1977 he was a research fellow at Har-vard studying nuclear-weapon proliferation.

Between 1979 and 1981 Leventhal was staff director of the Senate Nuclear Regulation Subcommittee, responsible for the investigations and legislation that led to two important nuclear laws. One was the 1978 Nuclear NonProliferation Act that imposed stricter controls on the US export of nuclear technology and nuclear materials to reduce the risk of the spread of nuclear weapons.

In 1979 and 1980 he was the co-director of the Senate Special Investigation of the Three Mile Island accident in 1979. The worst accident in a US nuclear power plant, it occurred in a civil nuclear reactor on an island in the Susquehanna River near Harrisburg, Pennsylvania. Leventhal prepared the legislation enacted in 1980 requiring preventive measures and emergency planning for future nuclear accidents.

In 1981, deciding that he could more effectively oppose civil nuclear power by establishing an independent research institute, Leventhal set up the Nuclear Control Institute to monitor global civil and military nuclear programmes, to develop measures to stop the further proliferation of nuclear weapons and reverse the nuclear arms race, and to evolve measures to prevent nuclear terrorism. Although the institute remained small it had significant influence.

Leventhal wrote and lectured widely about nuclear issues. He was a distinguished visiting fellow at the Global Security Programme at Cambridge University. In 2001 the Franklin and Marshall College awarded him an honorary doctorate.

A formidable, sometimes abrasive, opponent with considerable political insight, Leventhal always had a firm grip of the facts about any issue under discussion.

Leventhal’s wife and two sons survive him.

Paul Leventhal, campaigner against nuclear proliferation, was born on February 12, 1938. He died of cancer on April 10, 2007, aged 69