Astonishingly, the decision in 1958 to sell 20 tonnes of heavy water, a vital ingredient for the production of plutonium, appears to have been made by British civil servants with no input from ministers, the BBC report said.

The documents unearthed by BBC television's Newsnight programme, broadcast late Wednesday, show British officials decided that it would be "over-zealous" to insist Israel use the heavy water only for peaceful purposes.

Previously, America had refused to supply heavy water to Israel without such safeguards.

Heavy water is chemically the same as normal water, but where the hydrogen atoms are of the heavy isotope deuterium, in which the nucleus contains a neutron in addition to the proton found normally.

It can be used to turn natural uranium into plutonium, needed for nuclear weapons.

According to Newsnight, the 20 tonnes of heavy water was part of a consignment which Britain bought from Norway -- a pioneer in heavy water production -- in 1956, but which was later deemed surplus to requirements.

Although official papers initially presented the sale as a direct deal between Norway and Israel, memos in the National Archives in London reveal that the heavy water was shipped from Britain in Israeli ships in 1959 and 1960.

It was used for the production of plutonium at Israel's top secret Dimona nuclear reactor in the Negev desert.

The archives appear to show that the decision to sell the heavy water was taken only by civil servants, mainly in the Foreign Office and the UK Atomic Energy Authority, perhaps for economic reasons.