Simon Bridges has been accused of using fuel tax rumours in a "desperate" attempt to distract from the Jami-Lee Ross situation.
Under extreme pressure over his handling of the saga, he threw out a claim from an anonymous source that Wellington Council was in secret talks with the Government to implement one.
It's a claim the Government says is "completely fake, false information".
Mr Bridges was pleased with himself, saying the Government was now "on the ropes" over its new regional fuel tax plans.
"I've been told yesterday confidentially that Wellington Council is in secret talks with the Government right now to have a regional fuel tax in Wellington where prices are already sky-high," he claimed.
But he has no information to back this up, other than - ironically - an anonymous source.
"You tell me your sources, I'll tell you mine," he grinned. "I had a good faith basis on doing this."
And both Transport Minister Phil Twyford and Prime Minister Jacinda Ardern have ruled out the regional fuel tax spreading any further across the country.
"I can give this guarantee to this House and to consumers: there will be no other regional fuel taxes while I'm Prime Minister - which at the moment feels like it might be for a while," Ms Ardern said.
Mr Bridges tried to claim this as a win.
"They come down here, they make policy on the hoof," he told Parliament.
But Newshub understands the Prime Minister made the decision not to introduce any further regional fuel taxes way back when the legislation was being formed.
On September 18, a steering group made up of council representatives pitched the idea to Mr Twyford. On October 8 - more than two weeks ago - the Government ruled it out.
Ms Ardern says she was forced to clarify that today because Mr Bridges was being loose with the truth.
"The member is in the habit of mischief-making, throwing out this morning completely fake, false information," Ms Ardern retorted in Parliament.
And New Zealand First leader Winston Peters also accused a "desperate" Mr Bridges of "mischief-making".
Mr Bridges denied it was hypocritical to use secret sources when he ordered a witch-hunt into who leaked his expenses.
But leaks and anonymous sources are increasingly becoming a headache for the National leader.