Mortgage borrowers have never had it so cheap as they have in the last few months but not all of the banks have been playing hard to win over borrowers.

Three of the major banks are now offering ultra-low one year fixed term rates of 3.89 per cent while those who want to fix for longer over three years can secure 3.95 per cent - the first time three year rates have been below 4 per cent.

But research by the Herald shows some banks have been much more aggressive in acquiring new home loan business than others.

State-owned Kiwibank has made the biggest push growing its home loan book more than 9 per cent in the year to March 31 - much more than the market overall which is up 5.3 per cent to $260 billion.


But it remains a minnow compared to the Australian owned banks with less than 7 per cent of the home loan market.

BNZ, owned by Australia's National Australia Bank, has also been on a big drive to grow its loan book increasing it more than 8 per cent and taking its share of the mortgage market to 15.9 per cent as of March 31.

Bruce Patten, a mortgage broker with Loan Market, said BNZ had definitely been in acquisition mode and that had been driven by its re-entry into the broker market.

"That has been a real driver for them."

BNZ resumed dealing with mortgage brokers in 2015 after 12 years of not using them.

Mortgage brokers now account for 17.7 per cent of BNZ's mortgage origination, up from 13 per cent a year earlier, according to data released as part of its half year result last week.

Patten said BNZ had lost market share as a result of pulling out of the broker market and they were now trying to "claw back" what had been lost during that time.

It remains the smallest of the big four banks when it comes to home loans books.

ANZ is the largest with around 30 per cent of the market, while ASB has around 21 per cent and Westpac is just shy of 19 per cent.

Patten said Kiwibank was also using a limited number of brokers to boost its share but the bank had also been pushing its brand awareness under new chief executive Steve Jurkovich.

The interview: Steve Jurkovich - big ambitions for the people's bank

Patten said part of reason people had been moving to Kiwibank was price - competitive rates - and part of its was loyalty and citizenship.

"An incredible number want to bank with a New Zealand-owned bank."

But he said Kiwibank were also playing catch-up after losing momentum during a period when it had funding issues.

John Bolton, chief executive of Squirrel Home Loans, said there had been a definite shift to use more brokers with ANZ - the country's largest bank - reporting 41 per cent of its home loans being generated via brokers.

"If you went back seven or eight years ago it would be closer to 32 per cent."

Bolton said BNZ was getting more of its natural share of the growth because it was using brokers while Kiwibank was using brokers in Auckland where it has had poor market share.

In Australia around 60 per cent of all home loans are generated via brokers but it is lower than that here and thought to be around 40 per cent.

Bolton said the growth was not surprising given how much more difficult it was for people to navigate bank credit policies.

He said the other trends coming through in the last year was the decline in house sales in the Auckland market.

From the peak in 2016 the Auckland market was down around 35 per cent, he said.

There had also been a skew towards first home buyers playing a prominent role.

Kelvin Davidson, senior property economist at CoreLogic said first home buyers had been a key source of lending growth in recent months.

"So the banks targeting them in a big way will have been more likely to have grown market share.

"Geography may well play a role too – banks with larger presences in busy markets such as Wellington and Dunedin will have fared better."

The slowest grower has been Westpac whose home loan book grew 3.5 per cent in the year to March 31, slower than the 5.3 per cent market growth and just 1 per cent in the six months to March 31.

Westpac chief executive David McLean said it had grown at a slower rate than the market over the last six months after making an active decision to step out of the "intense competition" being seen.

"We are selectively choosing where to compete."

McLean expected the home loan market to grow at 4 to 5 per cent for the full year and said Westpac would definitely be back in the market in the second half of its financial year.

How to get a good deal on your mortgage

Squirrel's John Bolton said cash-backs were a big part of the market and should be taken into account as well as the interest rate as borrowers could shave up to 60 basis points off a mortgage rate by taking the cash-back into account.

He warned people against breaking their fixed term mortgage and said break fees would be higher because rates had fallen in the last year.

Make sure the numbers stack up before you leap.

But Bolton said those who are close to coming off a fixed term should look at trying to lock in a rate. This can be done up to 60 days ahead of the end of the term.

Bolton said switching banks may not be necessary to get a good rate and most of the banks were matching rates offered by other major banks.

First home buyers should get advice especially if they have a deposit of less than 20 per cent. Brokers can look at ways to boost the deposit through using parent's house or term deposits as security which can bring the rate down.

Bolton said people in their first home should try and get over the 80 per cent loan to value ratio as soon as possible to get a lower rate. This could be done through getting a house revaluation.