Green Party co-leader Russel Norman says incorrect reporting of figures relating to warrants and access authorisations by the government spy agency is further proof the public can have no confidence in it.
In its original report, the Government Communications Security Bureau said a total of 11 interception warrants had either been issued, or were in force, in the year ending June 2013. It also reported 23 access authorisations had either been issued, or were in force, over the same period.
That has now been changed to 16 interception warrants and 37 access authorisations - because it mistakenly recorded the number of operations it had carried out, as opposed to the actual warrants.
Dr Norman says it is hard to understand how the GCSB got this wrong.
"This is a critical issue. How many times are they going for warrants to intercept communications, how many times are they breaking into computers but they don't seem to have their head around the numbers, in spite of a legal requirement that they tell us what they're up to."
Prime Minister John Key has been sent a letter of regret over the misreporting from the head of the GCSB, Ian Fletcher. Mr Key said on Thursday he has received an assurance from Mr Fletcher that the mistake will not be repeated.
Deputy Prime Minister Bill English said while the blunder is disappointing it shows that the GCSB is operating in an more transparent manner, but it would have been better to get it right in the first place.