(Reuters) - ANZ Group ( ANZGF ), Australia's fourth-biggest lender, said on Thursday that a rise in mortgage restructuring contributed to a jump in asset impairments to their highest levels since 2021 in the first quarter.

While higher interest rates have boosted interest income on loans, they have also led to slower credit growth and increased bad debts, forcing banks to write down some of their asset values.

ANZ said its gross impaired assets increased to A$1.90 billion ($1.21 billion) for the three months ended December 31 - the highest since September 2021.

The bank's home loans in Australia with repayments more than 90 days late as a proportion of total loans fell by 1 basis point from September quarter, while those in New Zealand increased by 75 basis points.

ANZ said net loans and advances rose 4% in the quarter, with institutional lending accounting for a major portion of the growth. Its quarterly customer deposits also rose 2%.

The bank's common equity tier 1 (CET1) ratio, a closely watched measure of spare cash, stood at 11.5% at December 31, compared with 12.2% as at September 30.

($1 = 1.5765 Australian dollars)

(Reporting by Himanshi Akhand and Roushni Nair in Bengaluru; Editing by Anil D'Silva)