Simon Bridges is accusing Grant Robertson of smearing the National Party over the Budget leak.
- National leaks what it claims are Wellbeing Budget details
- Grant Robertson admits some Budget details National released are correct
- National's Budget 2019 drops could be the Government's greatest crisis
"The National Party has acted entirely appropriately," he tweeted.
"@grantrobertson1 has falsely smeared us to cover up his and The Treasury's incompetence. When what has occurred is revealed, he will need to resign."
Earlier on Tuesday, Bridges revealed details of the Wellbeing Budget, two days before the official announcements.
But Treasury says there's sufficient evidence to show this information came from its systems being hacked, and has referred the issue to the police.
Finance Minister Grant Robertson says it's an "extremely serious" matter and is calling on the National Party not to leak any more information.
“We have contacted the National Party tonight to request that they do not release any further material, given that the Treasury said they have sufficient evidence that indicates the material is a result of a systematic hack and is now subject to a Police investigation."
How did National get the details?
When asked if National found the information or was leaked it, Bridges said: "I'm not going to say how I got this information, just as I wouldn't expect journalists to do so."
"What we've done there, in the information that we've given you, is put together what we have from the information to protect how and what information we have, but it is certainly information from the Budget - we're confident of that."
"I think what it shows is a loose, incompetent Government that really doesn't know what it's about and what it's doing."
Treasury secretary Gabriel Makhlouf says the breach is serious, and the matter was referred to police on the advice of the National Cyber Security Centre.
"The Treasury takes the security of all the information it holds extremely seriously," he said on Tuesday night.
"It has taken immediate steps today to increase the security of all Budget-related information and will be undertaking a full review of information security processes."
He says there's no evidence personal information has been subject to the hack.