New Zealand's banking ombudsman received 283 disputes in the 12 months through June, rising 26% from the previous year to hit the highest volume in a decade, according to the ombudsman's latest annual report.

Among large lenders, ANZ Group Holdings (ASX:ANZ, NZE:ANZ) was part of 55 disputes, Westpac Banking (ASX:WBC, NZE:WBC) was involved in 39 disputes, and Commonwealth Bank of Australia's (ASX:CBA) ASB Bank was a party in 54 disputes, the report showed.

Meanwhile, 24 of the disputes were related to Heartland Group Holdings (ASX:HGH, NZE:HGH).

The ombudsman said overall, it received 1,822 enquiries and 3,310 complaints in the year through June, with scam-related complaints accounting for a significant portion of the total. The volume of financial hardship complaints remained steady compared with the previous year, but the number of such cases that resulted in a mortgagee sale increased.

On average, disputes were resolved 14 days faster than the previous year, with the average resolution time falling to 49 working days from 63. A total of NZ$1.3 million in financial compensation was awarded in the 12 months through June, the report showed.