Radio New Zealand reported the squad, which provides personal protection for New Zealand dignitaries and visiting guests of government, spent about $5.2 million in the year to June - $1.1 million over budget.
Duty minister Judith Collins said police had a budget of $1.4 billion a year so it was a small amount in the scheme of things, and police shouldn't have to put up with "nitpicking" comment around how they did their job.
"I would point out too there was in fact a Rugby World Cup during that financial year, there were a tremendous amount of dignitaries coming and going from New Zealand and, frankly, I would expect that the police should be allowed to get on with their job," she said.
"There's also things such as the election, and the leader of the opposition at the time, Phil Goff, he needed to have the diplomatic protection squad with him - possibly to protect him from his own colleagues."
She said Police Commissioner Peter Marshall was "very relaxed" about the situation.
Any further detail about what the money was spent on would have to come from him, she said.
Last year, the squad blew its budget by $800,000, $30,000 of which was used to send officers with Prime Minister John Key on his summer holiday to Hawaii.
- Matthew Theunissen of APNZ