National leader Bill English says he is disturbed a burst fuel pipeline has disrupted people's travel plans but he remains confident the situation will be rectified as soon as possible.

English said Air New Zealand had told him they were doing absolutely everything they could to accommodate disrupted passengers.

He made the comment to Newstalk ZB's Mike Hosking during the leaders' breakfast interview this morning.

English said the cost of installing a second pipeline would have had to be passed on to consumers so one had not been put in. It was the first time there had been a disruption to the supply.

He said another option was to increase storage at the airport so there were greater reserves.

English was also asked about Pike River and said he expected an unmanned re-entry into the mine by the end of the year.

"It will help them answer more questions, they want those answers and we've committed $5 million or so to help them get them."

On the Morrinsville farmers' rally today, English said the way some politicians had used the water situation had been "divisive" and farmers were aware of their responsibilities.

"Whatever divisiveness is there from this campaign I think will be fixed pretty quickly if we get on with the job."

English said he was enjoying the election campaign more than he'd expected and the level of public interest was higher than he'd seen in some time.

Household incomes were the main issue people raised with him on the campaign trail.

Asked by Hosking whether there was any point to the campaign rituals of walkabouts and selfies with people he'd probably rather not have to meet with, English hit back:

"I'm not sure how you feel about your listeners, but my voters, they're precious."

English said it ensured parties honed down their messages to voters.

"In this election it's got a whole lot of the public interested who probably haven't been interested in a while."

English was also grilled by Hosking on revelations last week that former Foreign Affairs Minister Murray McCully and his ministry had not received legal advice over the Saudi sheep deal.

English said the belief that New Zealand could have been sued by Saudi Arabia had prompted it to give an "agrihub" to a Saudi Arabian businessmen was based on McCully's "view".

McCully had said he went ahead with the agrihub to thwart potential legal action over New Zealand's ban on live sheep imports on the basis of legal advice.

It has since transpired there was no such legal advice. English defended McCully, saying he was entitled to reach such as conclusion as a minister.

"It's his view. He's entitled to take a view."

When questioned about unemployment English said he did not accept that there was a group of people in New Zealand who were just not willing or motivated to work, saying if those people were supported enough they could get jobs and stick to them.

He pointed to National's plan for more support but harsher sanctions for the young unemployed who either did not take up training or work opportunities or failed drug tests.

"Some of them are just cycling in the system, turning up and not going back.

"They can get in the door but they don't always turn up. If you can get them to stick for 12 months, then they'll stick in the job."

Asked about the difficulties some businesses were having in finding enough good staff, English said that was because the economy was working.

"It creates more jobs - we've got a higher proportion of our working population in work than before."

English also rejected comments by some business heads in the Herald's Mood of the Boardroom event that National was complacent and had missed opportunities, saying those were made by a few businesses who had been doing very well.

"One of those did let me know that when they went in to the ballot box, he voted National."

As an ad break began, Labour leader Jacinda Ardern's voice boomed out of the speakers as a Labour ad began - English laughed and pretended to wave at her.

During Ardern's own Leader's Breakfast last Monday, a National Party ad played.

English says Labour's proposal to renegotiate the Korean free trade agreement is a "crazy idea" and will ruin New Zealand's credibility.

"You would blow your credibility if you went back for a single domestic point. Because we are a small country with not much to offer them but who are always asking for things, we rely on our credibility."

Ardern has said she wants to renegotiate the recently signed agreement to allow for Labour's policy to ban foreigners buying property in New Zealand. Ardern believed South Korea would accept that given it had a similar protection for itself.

English expected South Korea would dismiss the idea given New Zealand had nothing to give back in return.

"They would say we are holding out against President Trump and the US which also wants to renegotiate its trade agreement with South Korea, and they would say bye bye."

Asked if he was embarrassed about the amount of money being splashed around in promises on the campaign trail, English said no - it was business as usual.

"What you are seeing here is two things - this has always been a busy Government, that's how you see projects like Waterview being completed ahead of time.

"The other aspect was that some of it was just people paying more attention to what the Government was doing. It had spent billions fixing schools over the last few years."

It was also important to set out what the government was doing, English said.