Intelligence heads are to be called together to Berlin next week and asked if they know who had planted the crude bug in the office of Wolfgang Neskovic, a Left Party member of the Bundestag parliament, German news agency DPA reported quoting senior legislators.

Neskovic works as the only Left Party member of a panel receiving regular briefings from intelligence services and is sworn to secrecy.

He is also a member of a special committee investigating why two Germans were put in U.S. prisons in Afghanistan.

Bundestag speaker Norbert Lammert said the bug did not work, "so it would not have been possible to listen in."

Parliamentary security experts were checking the capability of the device, which government sources said had not even been concealed.

Neskovic, who was traveling on a train, told Berlin newspaper the Tagesspiegal that he had no idea about the discovery of the bug.

The discovery has attracted outrage from officials of other political parties as Norbert Roettgen and Olaf Scholz, the whips of the Christian Democratic parties and the Social Democratic Party said that they had asked the permanent intelligence committee to investigate.