National Party MPs are denying any prior knowledge of the "verbal altercation" outgoing MP Nick Smith is under investigation for.
Smith will leave Parliament next week after 30 years, citing the loss of the Nelson seat at the election and an ongoing inquiry into an employment matter.
When announcing his sudden resignation last night, Smith said a Parliamentary Service investigation into the incident that happened in his Wellington office last July was still ongoing.
Smith said he regretted the incident and had apologised - but the best course of action was for him to resign.
National Party deputy leader Shane Reti said he did not know about the incident and only learned of the investigation on Monday.
"I was surprised. And then I pondered for a moment and then I got on with my work."
Reti said he had spoken to Smith since he announced his resignation but refused to say what was discussed.
He also refused to respond to questions about the "verbal altercation" and the Parliamentary Services inquiry.
He did, however, say he was confident the National Party did not have a bullying problem.
Smith would not be at Parliament this week, Reti said, and it was not clear if he would return at all.
National Party leader Judith Collins was also not at Parliament today because she was attending her son's graduation.
National Party president Peter Goodfellow said he also did not know anything about the spat and that Smith had not informed the party of the Parliamentary Services investigation.
Goodfellow denied party candidates had not been vetted properly before standing in the 2020 election, saying "we certainly did."
National Party chief whip Matt Doocey was the only MP who did know about the inquiry before it was made public, but could not say when he found out.
He also could not offer an explanation about why Smith was allowed to stand in the election.
"I was aware he was going through an issue with Parliamentary Services and it was up to Parliamentary Services to respond.
"We have a member of Parliament who's owned his behaviour and I acknowledge that."
The behaviour was "100 percent a once-off" and no other National MPs were currently under investigation, Doocey said.
"We expect a high level of professional, respectful and healthy and productive relationships between MPs and staff."
National MP Simon Bridges said no concerns about Smith's behaviour were raised with him when he was leader.
Other National MPs, including Andrew Bayly and Chris Bishop, were confident the party did not have a bullying problem.
When announcing his resignation yesterday, Smith said a media outlet had leaked details of the investigation into the altercation and was going to run a story today.
National Party MP Ian McKelvie questioned how details of the inquiry had been leaked.
"I don't know how something like that would get leaked and anyone who did leak something like that, if in fact it has been, is a disgrace to this place and certainly let the people who work in this building down."