The government says a statement on its response to the nerve agent attack in the UK was changed because of an editing error, but National called it doctored.
The statement condemning the attack was released last Friday under the names of Prime Minister Jacinda Ardern and Foreign Minister Winston Peters, but the entire text was attributed in quotes to Ms Ardern.
It was subsequently published on the Beehive website under the heading Joint Statement, with the quote marks removed.
"Someone snuck in and secretly doctored the statement," National's foreign affairs spokesman Todd McClay said today.
"Does this mean the prime minister is backing off her statements, or that the foreign minister has changed his mind?"
A spokesperson for Ms Ardern said attributing the quotes in the first statement to Ms Ardern had been an error.
"It was an editing mistake, quickly picked up and corrected," the spokesman said.
Before the statements were issued, questions had been raised about Mr Peters' attitude to Russia.