Embarrassing errors in basic information supplied by the GCSB spy agency to Parliament have given Labour and the Greens fresh ammunition to back their call for a full inquiry into all of New Zealand's spy agencies.

Greens co-leader Russel Norman said the information was "bread and butter stuff".

"They should not be getting this sort of thing wrong."

Labour leader David Cunliffe said the blunder would "do nothing to reassure Kiwis their spy agencies are competent".

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The Government Communications Security Bureau tabled a correction in Parliament yesterday to the annual report which contained a basic error in the number of interception warrants (for bugging phones) and access authorisations (for watching computers) issued and in force in 2012-13.

The mistake was in supplying the number of operations conducted during the year rather than the number of warrants and authorisations. Some operations had several warrants.

GCSB director Ian Fletcher sent a letter of apology to the responsible minister, Prime Minister John Key.

Mr Key was unhappy with the errors and described them yesterday as "embarrassing".

He gave repeated assurances last year that the agency was operating more effectively after revelations of unlawful surveillance prompted a compliance review by Rebecca Kitteridge, the Cabinet Secretary who will take over the SIS this year.

The review and subsequent reforming legislation followed revelations the GCSB had unlawfully spied on internet mogul Kim Dotcom in an advance of an FBI raid on his Coatesville mansion.