Foreign Minister Murray McCully says his own department was to blame for the delay in finding out how the US travel ban would impact on New Zealanders.
It took five days for MFAT to discover that New Zealanders holding dual citizenship of Iran, Iraq, Libya, Somalia, Sudan, Syria and Yemen would not be barred from entering the US.
Britain, Australia and Canada were reported to have been informed earlier that their dual citizens would be exempt.
Mr McCully summoned MFAT chief executive Brook Barrington to the Beehive on Wednesday for a dressing down.
"I wanted to convey unambiguously the expectations I have on behalf of the government," he told RNZ on Thursday.
"I don't think they have met the standards the prime minister and my colleagues would have expected ... we haven't done ourselves any favours in the last couple of days."
Mr McCully says substantial change is going on in the US and it's a challenging situation for other governments, but that can't be used as an excuse.
"The ministry needs to meet certain standards, get answers and interpret what's going on."
Prime Minister Bill English on Wednesday said it had been "a frustrating few days" but he defended New Zealand's ambassador to Washington, Tim Groser.
"I think our ambassador's doing a fine job," he said.
"It would have been better to know a day or two earlier and we've learnt for next time about not to assume they're going to tell us, you have to go after it."