Secret documents found in an al-Qaeda safe house in Kabul, purporting to reveal Osama bin Laden's nuclear plans, have been revealed to be nothing more than a spoof that has been circulating on the internet for years.

According to Jason Scott, a reporter for the website rotten.com, phrases used in the documents, which were discovered after the Taleban fled the capital, were the same as ones used in a 1979 parody on scientific publications known as The Journal of Irreproducible Results.

The original, entitled How to Build an Atomic Bomb in 10 Easy Steps, explains how to create a device for between $5,000 and $30,000 that "is a great ice-breaker at parties and, at a pinch, can be used for national defence".

With the advent of the internet, the journal has been passed around much like an email chain letter.

It is thought that al-Qaeda is desperate to get hold of any information it could use for its acts of terrorism, but it also suggests that the group had very little idea of what it was doing and had no sense of humour whatsoever.

A BBC report showed a paragraph that described the implosion principle by which a nuclear fission weapon is triggered. But the next paragraph in the parody reads: "In next month's column, we will learn how to clone your neighbour's wife in six easy steps."