The move comes after reports that the BND agency had kept journalists under surveillance and allegedly paid others to spy on colleagues to trace leaks.

Some leading German news organisations, including Der Spiegel, have admitted some staff members worked for the BND as recently as last year.

The BND is already under investigation over its agents' role in the Iraq war.

A parliamentary committee is investigating claims that two German agents in Baghdad shared intelligence with Washington at the start of the 2003 war - which the German government at the time had publicly opposed.

Government spokesman Ulrich Wilhelm told a news conference: "The chancellery ordered the BND today not to undertake operative measures against journalists for its own protection."

He said the new measure covers the BND's protection of its own work on German soil, but journalists could still be used as sources in its foreign operations.

The agency is expected to answer questions set by MPs this week.