Senior National MP Judith Collins said that Jami-Lee Ross' tweets openly undermining Leader Simon Bridges were "appalling" and has said Ross should have come forward as the leaker sooner.
She had also told the Herald she would not have put up with Ross' behaviour "if I was in his [Bridges] position."
Earlier today, a report into the leaking of Bridges expenses in August found that on the balance of probability, it was Botany MP Jami-Lee Ross who leaked the information.
Moments before Bridges spoke to media, Ross took to Twitter to say Bridges was about to "attempt to pin his leak inquiry on me" as he was not able to "find who the actual leak is".
"Some months ago I fell out with Simon. I have internally been questioning leadership decisions he was making, and his personal poll ratings which show he is becoming more and more unlikable in the public's eyes."
National's caucus will discuss whether or not to suspend Ross from the caucus tomorrow morning.
Collins said the PWC report on the leaked expenses "speaks for itself" and has slammed Ross' tweets.
"What's been said today on Twitter is pretty appalling."
"I would not put up with it if I was in his [Bridges] position."
She said Ross should have come forward sooner, given "every other member of the caucus has had their privacy breached," she said in reference to the PWC report.
All National MPs had to let investigators look through their emails and texts.
North Shore National MP Maggie Barry said she is "extremely disappointed to see disloyalty on this scale" by Ross.
Asked if she will vote to suspend him, she said she would wait until she has seen the full report.
But she had praise for her leader as to how she thought he handled the process.
"Bridges has done well, given the circumstances."
National Deputy Leader Paula Bennett would not be drawn as to whether she would vote to suspend Ross, saying it was a "caucus decision".
She said she "absolutely stands behind" Bridges' as leader.
National list MP Alfred Ngaro said the discussion about Ross' suspension will happen inside caucus tomorrow – "it's a conversation that will happen behind closed doors".
He said he supports the Party's leadership – "we needed to get this sorted out, that's the reason we had the inquiry".
"Now we have got the report, he [Bridges] is doing the right thing by taking it back to caucus as the leader and for us to discuss it.
"I definitely back him in the process of what we're doing at the moment."
National MPs Paul Goldsmith and Parmjeet Parmar did not want to comment.
Tomorrow morning, the National Party caucus – the 56 MPs that make up the sitting MPs of the Party – will discuss Ross' political fate.
It will be up to MPs as to whether to suspend Ross' from the caucus.
As for further steps, that's where the National Party board will take over. It will be up to its members, led by Peter Goodfellow, to decide if he will be suspended, or expelled, from the National Party.
Bridges said he briefed the board on the PWC report's findings before he spoke to media this afternoon.
As well as discussing the leak, Bridges said caucus will also discuss "other issues around his [Ross'] conduct"
'[MPs] will consider the matters that are relevant to them – there is a bunch of options available to them.
"We will be having a discussion on all relevant matters – which includes a pattern of conduct."
However, Bridges would not go into detail about what "other issues" entailed, only that MPs will be asked to consider if there was a "pattern" of behaviour.
If National's caucus does decide to suspend Ross, he will still sit in Parliament as he won his electorate seat in Botany last election.
However, he would likely be stripped of any National Party responsibilities – he had previously been the party's spokesman for Transport – and sit on the backbench.
If Ross decided to step down as an MP, that would force a by-election in Botany.
Being suspended, but still remaining in Parliament, is not unprecedented – this happened to National's Maurice Williamson in 2003 after he undermined then leader Bill English.