A document which is said to detail a step-by-step guide on how to build an atomic bomb has been removed from a public office.

BBC News Online reported on Monday that the file, which was in the archives at the Public Record Office, gave measurements, diagrams and precise details on bomb-building.

As a result of publicity about the document, the Ministry of Defence (MoD) sent a representative to the office who has now removed it.

A spokesman said: "There is one document that has been withdrawn.

'Monstrous'

"It is being looked at, as well as the reviewing the process documents go through before they are put out to the public."

She stressed that the process was "very stringent and very formal".

Shadow defence secretary Bernard Jenkin had criticised the document as a "monstrous free gift to terrorists" and called for an immediate government investigation.

He told BBC News Online: "The fact that this information has been lying in the public records office is extraordinary.

Smuggled

"Such information may already be in the public domain, but why needlessly help rogue states and terrorist organisations with such comprehensive instructions on how to make an atom bomb?

"I will be pressing the government for a comprehensive explanation."

The files are said to relate to the construction of Blue Danube, the first British atomic bomb, which was built in the late 1940s and early 1950s.

It is also said to describe various ways in which such a bomb could be smuggled into the country.