National party leader Todd Muller seemed somewhat bemused as reporter's grilled him over disgraced Hamish Walker's resignation — at a press conference that was meant to be about the $1.5 billion 60km expressway between Ashburton and Christchurch.

Earlier today, Muller said he had accepted Walker's resignation after the MP admitted to leaking the personal details of 18 Covid-19 cases to media.

Possibly thinking that his part was over and done with his statement this morning, the National leader arrived in Ashburton for a South Island roading announcement.

But when it came to question time, he was bombarded with questions about the Covid-19 leak scandal.

He responded to many questions about Walker before he visibly had had enough.

"Any questions about the road?", he said smiling and looking around as everyone can be heard awkwardly laughing.

"Come one, $1.5 billion four-lane highway. Fantastic."

a truly iconic moment in #nzpol https://t.co/C4M7vhVRIt

— David Cormack (@David_Cormack) July 8, 2020

This is much worse than I imagined it

— Hayden Donnell (@HaydenDonnell) July 8, 2020

People on social media have branded the remark as "embarrassing" while political commentator David Cormack said it was "a truly iconic moment in #nzpol."

Meanwhile, Herald political reporter Jason Walls took note of National MP Gerry Brownlee's facial expressions during this press conference.

Living for the Gerry Brownlee facial expressions during this press conference, where National leader Todd Muller said now ex-MP Hamish Walker had ‘paid the ultimate price’. pic.twitter.com/K3A4lkmRL0

— Jason Walls (@Jasonwalls92) July 8, 2020

During the press conference, Muller told reporters: "Hamish has decided not to stand again ... it's the right decision and now we look forward to identifying [a new] candidate."

"His judgment was fundamentally flawed."

Muller said it was not true to say that National had a track record of "dirty politics".

"One MP made a serious error and has paid the ultimate price," Muller said.

Muller reiterated his earlier statement that he only became aware of the privacy breach at midday on Monday.

Former National Party president Michelle Boag, who gave the patients' details to Walker, had recused herself from any active role in the party, which showed how serious the issue was, Muller said.

The leaking of that personal information was "totally inappropriate".

"Of course I apologise."

At the beginning of his announcement on South Island transport, Muller said National will build the Christchurch to Ashburton Expressway, originally announced as one of 10 "roads of national significance" by National in August 2017.

He said building the four-lane expressway between Christchurch and Ashburton would begin in National's first term with construction likely to start after 2023, at a cost of $1.5 billion.