An official who left secret files on al-Qaeda and Iraq on a train should not have had them in public, the Government said.

Cabinet Office minister Ed Miliband said a full inquiry had been ordered into the "clear breach" of security rules by the individual, who has been suspended.

He insisted national security interests did not appear to have been damaged or operations and individuals put at risk.

Mr Miliband refused to be drawn on a suggestion by Labour MP Andrew Mackinlay that the unnamed official who left the documents on the train was an MI5 officer on secondment to the Government.

He has been described as a senior civil servant working in the Cabinet Office's intelligence and security unit, which contributes to the work of the Joint Intelligence Committee.

It is understood his work involves writing and contributing to intelligence and security assessments and that he has the authority to take documents of this sort out of the Cabinet Office, as long as strict procedures to ensure their safety are observed.

One of the lost documents was a seven-page report on "Al-Qaeda Vulnerabilities" and is understood to look at the state of the Islamist terror network in Afghanistan and Pakistan.

It was classified "UK top secret" and considered so sensitive that each page was numbered and marked "For UK, US, Canadian and Australian eyes only".

The second document was a "top secret and in some cases damning" assessment of Iraq's security forces, according to a journalist who read it.

The loss came to light after the files were found by a member of the public in an orange cardboard envelope on a train from London Waterloo to Surrey.

Mr Miliband said: "This was a clear breach of well-established security rules which forbid the removal of documents of this kind outside secure Government premises without clear authorisation and compliance with special security procedures."

He added: "No authorisation was sought for the removal of the documents.

"While the documents do not contain the names of individual sources or specific operational details, they are sensitive, high-level intelligence assessments.

"There is no evidence to suggest that our vital national security interests have been damaged or any individuals or operations have been put at risk."

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