Police Minister Stuart Nash believes an investigation will show other National Party MPs or members were also involved in Covid patient data leak.

Last night, MP Hamish Walker and former National Party president Michelle Boag confessed to being behind the massive privacy breach of Covid-19 patient information.

"I simply can't believe that this is just Michelle Boag and Hamish Walker. They'll be others' fingerprints all over this," Nash told Newstalk ZB this morning.

"Bill English and John Key would have handled this completely differently. This is a National Party problem at this point."

National MP Mark Mitchell told Newstalk ZB's Mike Hosking Breakfast his party should deselect Walker as the candidate for Clutha Southland.

"Ultimately it's a decision for our board and the leader, but I think that it's a massive departure from our own set of values and what we stand for in the National Party.

"My own personal expectations would be that Hamish wouldn't be standing. It's sad, because he's done an outstanding job of advancing issues for his electorate, but he's shown a terrible lack of judgment on this one."

Mitchell said should be reflecting on whether he should voluntarily stand down as an electorate candidate.

"It's terrible, difficult situation. He's got a young wife, he's got a new young daughter, but there's no excuse for leaking personal information, so I hope he is reflecting on that today."

Mitchell said it is up to the board to discuss Michelle Boag's future in the party.