40 years on, Pentagon Papers are public

The top-secret document shocked America with its disclosure of presidential lies and official subterfuge after sections were slipped to journalists at the New York Times in 1971.

Four decades on, the 7,000-page report has finally been put on record in its entirety.

At noon yesterday, the US National Archives and presidential libraries started allowing members of the public to review hard copies, while its contents were also posted online.

Around a third of the contents of 48 boxes of documents are being opened for the first time. But the whistleblower behind the original leak, Daniel Ellsberg, warned that chances of finding new revelations were slim.

Most of the secrets contained in the report of the Office of the Secretary of Defence's Vietnam Task Force - to give the Pentagon Papers their official title - were given up long before they were put on public record.

Mr Ellsberg, a former government military analyst, began surreptitiously photocopying documents in 1969 after turning against US involvement in the south east Asian conflict

On 13 June, 1971, the New York Times started publishing reports based on the papers leaked to them by Mr Ellsberg.

It chronicled decades of creeping US involvement in Vietnam and exposed how the US had deliberately provoked strikes from the Communist north to justify American participation.

Later reports based on the Pentagon Papers detailed how the public and Congress had been deliberately misled by Presidents Lyndon Johnson and John F Kennedy.

The documents also contained information suggesting that casualty figures could be far higher than publicly disclosed.

Coming at a time when the popularity of US involvement in Vietnam was already waning, the papers were seized on by anti-war protesters.

At the time, then-president Richard Nixon was initially delighted that people were reading about bumbling and lies by his predecessors, which he thought would take some anti-war heat off him. But if he loved the substance of the leak, he hated the leaker.

He called the leak an act of treachery and vowed that the people behind it "have to be put to the torch".He feared that Mr Ellsberg represented a left-wing cabal that would undermine his own administration with damaging disclosures if the government did not crush him and make him an example for all others with loose lips

The leak ultimately provoked a bitter legal battle between Nixon's administration and the media, which the White House eventually lost.

After an initial injunction, the Supreme Court ruled in favour of the New York Times and Washington Post, claiming that newspapers had the right to report on the leaked documents under the First Amendment, which ensures freedom of speech.

Meanwhile, an attempt to prosecute Mr Ellsberg over the leak fell apart after White House agents were found to have broken into the office of the whistleblower's psychiatrist in a bid to get discrediting information.

The break-in was a precursor of the dirty tricks operations employed by the Nixon administration, which were eventually to bring down the president in the Watergate scandal.

During interviews marking the fortieth anniversary of the initial New York Times report on the Pentagon Papers, Mr Ellsberg said his only regret is that he didn't blow the whistle on the government earlier.

"Don't do what I did. Don't wait until the bombs start falling," he offered as advice to today's whistleblowers.

The 80-year-old has recently spoken in support of Bradley Manning, the US army private thought to be behind the WikiLeaks cables.

In March, Mr Ellsberg was arrested while protesting outside Quantico military prison, where Mr Manning was being held.