Things are looking up for home-hunters who can't afford a 20 per cent deposit, as banks increasingly relax their purse strings.

Reserve Bank figures show banks loaned $484 million to low-deposit borrowers in May, up from $390m in April.

That is the highest sum banks have loaned out in a month since Reserve Bank restrictions were introduced in October 2013.

However, availability is still nowhere near what it was before the rules, when banks were lending well over $1 billion a month.

Low deposit loans accounted for 6.8 percent of total mortgage lending in May, excluding exemptions for the likes of new builds.

While that remains well below the Reserve Bank's 10 per cent limit, it continues the slight easing trend of recent months.

First-home buyers took out 36 per cent of the low deposit loans, compared with property investors' 12 per cent share.

However, investors borrowed $1.98b of overall mortgage lending, more than three times as much as first-home buyers.

The Reserve Bank's rules were designed to take some heat out of the property market and protect the stability of the financial system.

While banks have toed the line and reined in their lending significantly, house price inflation is still running hot in Auckland, prompting more action from the central bank.

From October, investors in the country's biggest city will be all but barred from borrowing without a deposit of at least 30 per cent .

The bank is also considering imposing income caps that would restrict how much people can borrow depending on their income.