Thatcher refused to sanction criticism of French over sinking of Greenpeace ship, archives showRead the documents here

Margaret Thatcher refused to sanction official criticism of the French over the blowing up of the British-registered Greenpeace ship Rainbow Warrior even after Paris had admitted being behind the bombing, newly released documents show.

The then prime minister sided with the foreign secretary, Geoffrey Howe, who did not want to "rub salt in French wounds", despite calls from cabinet colleagues who thought the government should take a firmer line.

The then transport secretary, Nicholas Ridley, described the incident as "an outrageous act of terrorism".

The papers also show that the Thatcher government refused to hold an inquiry into the sinking, as it had the power to do, but kept this decision secret until the public outcry had faded.

French secret agents blew up the Rainbow Warrior to prevent Greenpeace protesting against the testing of nuclear weapons at Mururoa in the South Pacific.

The bombing of the ship when it was moored in Auckland harbour, New Zealand, in July 1985 killed one of the crew and brought protests from around the world.

Greenpeace's campaigns director, Blake Lee Harwood, said yesterday: "The Thatcher administration was famously unsympathetic to Greenpeace and so their action in downplaying an act of state terrorism and murder was entirely in character. However, 20 years on, remaining mute in the face of the blowing up of a peaceful ship in the harbour of a Commonwealth country seems strangely at odds with Tony Blair's war on terror."

The documents, released to Greenpeace under the Freedom of Information Act, show that when the French admitted after two months that they were responsible for the bombing, Mr Howe wrote: "We have no wish to rub salt in French wounds, nor do we wish to appear more aggrieved than Greenpeace. We took care to avoid impugning France prior to the official French admission of responsibility."

The documents also show that Mr Howe intervened to tone down criticism of the French.

John Prescott, then an opposition MP sponsored by the National Union of Seamen, had written to Mr Ridley calling on the government to condemn this "act of war" and launch an inquiry.

The Rainbow Warrior was registered in Aberdeen. Under maritime law, the British government had the right to investigate the loss of any British-registered ship, but was not obliged to do so.

According to a transport department memo, Mr Ridley at first told his officials of "the need he saw for a robust attitude by the government to the sinking".

"The two key points he felt should be included in the reply to Mr Prescott were the government's condemnation of this act and the government's readiness if appropriate (ie, essentially, in relation to any French government involvement) to seek compensation as a manifestation of diplomatic protection of British interests."

Mr Ridley's officials drafted a reply to Mr Prescott saying: "This was an outrageous act of terrorism against a British vessel with tragic loss of life, which the government utterly condemn." It refers to Fernando Pereira, the photographer who was killed, as a "murdered man."

Three days later, a Foreign Office official wrote to the transport department, saying that Mr Howe had seen the draft and suggested a softer response, which was eventually sent to Mr Prescott: "This was a lamentable event. The government deeply regret the death of a member of the crew. We hope the culprits can be brought to justice."

Davey Edwards, the engineer of the Rainbow Warrior and the only British crew member, told the Guardian this year that he remained angry that he had not received any diplomatic support from the government, any financial help, or even a new passport, and that no public protest had been made about an act of terrorism and murder.

The documents also show that British diplomats agreed that it was in Britain's interest for the French and the New Zealand government, which was furious at the bombing in its waters and was trying to prosecute the perpetrators, to patch up their differences and seek a way of ending the controversy.

One wrote: "I share the view that it is in our own and the general western interest for France and New Zealand to seek an accommodation now that [the French prime minister] Fabius's frank if tardy admission of French guilt has terminated the lies and evasion and opened the way for more constructive moves."