"terrorist investigation" has the meaning given by section 32 of the Terrorism Act 2000.

After the agent's memorandum arrived at headquarters, it was sent to the bureau's New York field office, which then had the lead in international terrorist investigations.

"This is the fruit of one of the most exhaustive terrorist investigations we have had since I have been in office," he said.

Material retained under this paragraph must not be used other than - in the interests of national security, or for the purposes of a terrorist investigation.

Section 215, which gave the government increased powers to gain access to records to assist in terrorist investigations.

It makes sense to promote greater sharing of information obtained in terrorist investigations, for example.

Most were for help in regular criminal investigations and only a handful involved aiding the authorities in terrorist investigations.

The law provides for the special status to be given to only 50 people a year who help in a terrorist investigation.

"The terrorist investigation has generated additional cases that we may not have run across in the normal course of events," Mr. Johns said.

"Media characterizations of this as a terrorist investigation are premature."