Britain admitted Friday that it knew that heavy water it sold in the 1950s, a key ingredient in making nuclear weapons, was bound for Israel, amid claims of a cover-up.
An investigation by BBC television's "Newsnight" programme unearthed papers showing a deal was done to export heavy water.
The probe showed that "Britain knew that the heavy water was going to Israel and that the Israelis were likely to use it to make nuclear weapons," alleged BBC reporter Michael Crick.
Britain's Foreign Office minister Kim Howells has insisted that Britain had merely negotiated the sale back to Norway of surplus heavy water. That surplus was then sold on to Israel.
Officials had added that they were unaware that Israel might have has nuclear weapons ambitions.
However, a Foreign Office spokesman, while maintaining that it was purely a deal between Britain and Norway, admitted Britain knew the heavy water's final destination.
"The papers show that we agreed to transfer back to Norway control of 25 tons of heavy water," the spokesman told the BBC. "We were aware at the time that Norway planned to sell the heavy water to the Israeli Atomic Energy organisation," he said, going further than Howells.
The BBC said new documents had emerged which cast doubt on claims that British officials had no idea of Israel's intentions.
In 1958 Britain's Atomic Energy Authority (UKAEA) wrote to Foreign Office official Donald Cape, who gave the ministry's approval for the deal.
Britain had seemingly bought too much heavy water from a Norwegian company and wanted to sell the surplus.
According to one letter, UKAEA said another Norwegian company, Noratom, wanted to purchase it to sell it on to Israel.
"The new customer is the Israeli atomic energy organisation," the letter said, according to the BBC. This would put Britain in a tricky position as "it could be argued that the Israelis will receive the heavy water by reason of our reselling it to Noratom; that therefore we are parties to the supply to Israel". "Newsnight" also said it had a copy of Israel's contract with the Norwegian firm which said it would provide heavy water from the UKAEA.
The programme said it had seen a letter written by Cape quoting secret US Central Intelligence Agency reports from 1957 and 1958, which took the view "that the Israelis must be expected to try and establish a nuclear weapons programme as soon as the means were available to them".
The confidential documents also apparently show that the Foreign Office knew Israel was secretly trying to buy uranium from South Africa.
Other secret government documents apparently say: "It has been, and remains our opinion, that Israel wanted an independent supply of plutonium so as to be in a position to make a nuclear weapon if she wished." Cape denied the sale back to Norway was a "sham" and said officials at the time did not suspect that Israel hoped to manufacture nuclear weapons.
The programme alleged that Britain took the heavy water out of its military stockpile and loaded it onto Israeli ships at a British port in June 1959 and June 1960.