Exactly 20 years after the bungled operation in Auckland harbour, a report by Admiral Pierre Lacoste, who at the time was head of the DGSE, the French foreign intelligence service, was published by Le Monde. In Operation Satanic, as the DGSE called the plan, three teams of secret agents used explosives to sink the vessel as it was preparing to sail to observe French nuclear testing at Mururoa atoll in the Pacific. Fernando Pereira, a Portuguese photographer, died in the attack.

In a scandal that continues to haunt France’s relations with Australasia, New Zealand arrested two DGSE officers who were posing as tourists. They were sentenced to long jail terms, but handed back to France in 1986.

M Mitterrand and his ministers denied any knowledge of Operation Satanic, which they put down to rogue agents. The President ordered an inquiry to “find out the truth”. It whitewashed the Cabinet, but MMitterrand sacked Charles Hernu, then the Defence Minister, and Admiral Lacoste.

In the admiral’s memorandum, which, the newspaper said, was prepared a year after the attack but did not surface till this weekend, he wrote that M Hernu had ordered him to “neutralise” the Rainbow Warrior because it was vital for national defence to prevent the environmentalist organisation from disrupting the nuclear tests. “They are waging war against us. We cannot have scruples about such a vital subject,” the minister told Admiral Lacoste.

The admiral wrote that he had sought confirmation from M Mitterrand that the risky operation had been authorised. The President received him on May 15: “I asked if he was authorising me to execute the project of neutralisation. He gave his agreement, stressing the importance that he attached to the nuclear tests. The authorisation was sufficiently explicit.”

The admiral described how the Defence Minister had assigned £300,000 from secret funds for the mission, which was also approved by the Chief of Defence Staff. When the Greenpeace affair broke with the arrest of the French agents, M Mitterrand, Laurent Fabius, the Prime Minister, M Hernu and senior staff denied any knowledge. “There was an easy way for them to find out from day one; they only had to summon me. Not only was I never summoned, but they always refused to let me (testify) when I asked,” wrote the admiral. His report, with its first-hand account of the planning, confirmed longstanding suspicions that the late Socialist President must have been involved.

The sabotage was the first of a string of scandals that tainted M Mitterrand’s presidency.

Yesterday Greenpeace held a rally in Paris to commemorate Senhor Pereira, who was 35 when he drowned in the sinking boat. He had returned to the vessel to save his cameras after a first explosion, intended to force the crew to flee before a second, more powerful charge holed the boat.

Senhor Pereira’s widow has received neither an apology nor compensation from the French Government.