Simon Bridges has taken a dig at former National Party leader Todd Muller, saying he "wasted" valuable time during his swift term as leader.

Talking to Heather du Plessis-Allan, Bridges said he was disappointed with Muller's stint at the top and how the leadership coup played out.

Bridges says the party's election preparation was hindered but believes the rise of Judith Collins could propel the party forward to success.

"I was really disappointed [in how the leadership coup played out]. It would have been a privilege to lead National into this election.

"We wasted a bit of time. There's a bunch of complex reasons for that.

"We're making back that time. We're going to finish this election much more strongly than the position we were in two or three weeks ago."

Bridges has since risen from the ashes after he was booted out as leader of the National Party two months ago, but is now back at number four in the party shadow cabinet having been handed the foreign affairs and justice portfolios.

When asked about tackling the new portfolios, Bridges said he feels he can make a difference given it's his area of expertise.

"I feel really good about it. When Judith Collins called me and offered me justice and foreign affairs I said yes. Justice is a returning home for me because it is my professional background."

While Bridges rose to number four, Collins was handed a blow after Nikki Kaye and Amy Adams both confirmed their resignations and will not contest the September election.

Collins insisted that Kaye and Adams leaving was not a sign they couldn't work under her leadership.

Despite National losing two of its most senior party members, Bridges told Newstalk ZB National are in a stronger position than they were previously.

He went as far as saying Collins will give Prime Minister Jacinda Ardern a tough run and believes Kiwis will like what the new National leader brings.

"The reality is we are the underdog but we are stronger than we were four weeks ago.

"We're on the comeback trail. Even as the underdog we have a path to victory."

"Under Judith Collins you're not going to be left wanting to know what we think. There will be a contest and you will have a very clear choice at this election.

"I think we can [win]. It will be harder than perhaps it was. Prior to Covid we were in the mid 40s. Covid came along and people have rallied to the Government. We've had our issues. It's been a bruising time for National.

"We've got a new leader, people know her experience, they know her toughness, they know what she's about and we do still have a strong team.

"Literally as soon as tomorrow morning from Judith's announcement on infrastructure, you'll see us rolling things out. Whilst we are the underdog we've got a real chance of winning this election."

Asked whether National are in a better position now than when he was leader of the party, Bridges said the right person is currently in the job.

"I don't know. People can have their different views. We are where we are.

"Judith is our leader and she's going to do a really good job. Right here right now, for what we need, Judith is our person for the hour. New Zealanders won't be left wondering."