A $180 million accounting error at the Ministry of Transport last year was not discovered for six months, and eventually led to the resignation of one worker.
Ministry chief executive Martin Matthews revealed details about the mistake at a parliamentary committee hearing this morning, saying the matter had been dealt with with the "utmost seriousness".
The error occurred when a figure was left out while data was being transferred between spreadsheets, leaving the New Zealand Transport Agency (NZTA) apparently up $180m.
"The effect of that error was that for a period of time the NZTA believed it had more money in the bank than it did," Mr Matthews said.
"Both the NZTA and and we took this extremely seriously ... The staff member who made the accounting error took it so seriously that he resigned and has left the ministry."
Mr Matthews assured the committee there had been changes made to prevent future errors.
"With the NZTA, we commissioned a major review of the cash management processes end to end since then, and they have now been significantly strengthened."
Speaking to APNZ outside the committee, Mr Matthews said he could not remember the date the error was made, but said the ministry had caught it six months later.
"What it meant was that, because the agency thought it had more money for a while, it was able to anticipate that it could do more than it could," he said.
While none of the money was spent and the mistake had only affected planning, Mr Matthews said the ministry was not resiling from the seriousness of the error.
"We were quite transparent about it when it occurred, we put our hands up and said 'this accounting error has occurred, it's been fixed' ... and as I say, that staff member resigned."