The police, armed forces and intelligence services were all mobilised following the "very successful" practical joke made during a student rag week, said the files released by The National Archives.
They revealed how the authorities, including four local forces and a bomb disposal unit, swung into action after calls from the public that six "flying saucers" were found in a perfect line across southern England, the Telegraph reported.
"But fears of a real 'war of the worlds' incident petered out after examination of the 'spacecraft' showed that it was an elaborate rag week hoax by engineering students," said the newspaper.
According to the files, early in the morning of September 4, 1967, the police and RAF were flooded with calls from the public reporting six small "flying saucers" that had been discovered in locations in a perfect line across southern England from the Isle of Sheppey to the Bristol Channel.
Four police forces, bomb disposal units, the army and the intelligence branch were all mobilised, before it emerged the saucers were a hoax by engineering students from Farnborough Technical College. The joke was only discovered after bomb disposal experts opened up one of the objects and found it was a fake.
The story emerged as part of the largest ever release of UFO files, which also revealed a number of military sightings of UFOs, a claimed "alien abduction" in London and an unidentified aircraft shadowing a Lancaster bomber.
They also disclosed how the phenomenon was discussed at the highest level of government and security services worldwide, including at the UN, the US Central Intelligence Agency (CIA) and was even the subject of a debate in the House of Lords.
The previously-classified records showed that in January 1979, the House of Lords held a debate of the subject of UFOs -- the only full debate on UFOs ever held in UK Parliament. In another incident in December 1977, the files said, the Government used its influence to talk down a call by Grenada President Sir Eric Gairy for a UN agency to conduct research into UFO sightings.
Sir Eric eventually withdrew his proposal but continued his campaign for a full UN debate on UFOs, calling on the UN General Assembly to make 1978 "the year of the UFO".
One of the 35 newly-released files shows 15 unidentified aircraft were detected on radar approaching the UK between January and July 2001 in the months leading up to 9/11.
According to the files, the Ministry of Defence even received one UFO report (with no radar corroboration) on September 11 itself.