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The Government is tight-lipped about the reported discovery of a listening device during sweeps for bugs at government ministers' homes.

Government Communication Security Bureau (GCSB) searches were done following fears surveillance devices had been planted ahead of the November election, The Sunday Star Times reported.

Government sources said that ministerial homes and offices have been swept, sometimes secretly, and at least one listening device was found.

GCSB ensures politicians are free from intrusion, and staff inspect New Zealand embassies and offices around the world.

Prime Minister John Key's office would not comment on the discovery.

"We really don't talk about this type of stuff. We don't comment on security matters," chief-of-staff Wayne Eagleson said.

Police Minister Judith Collins was also keeping mum. "It is not something I can discuss."