Suncorp sustained a 28% fall in net profit to $382 million in the six months to December 31, with severe weather contributing to a 55% drop in general insurance income.

CEO John Mulcahy defended the company's performance, telling analysts it was due to volatile credit and equity markets.

"It has been perhaps the most challenging and demanding [period] in Suncorp's history," Mr Mulcahy said.

The company's general insurance division had pre-tax profit of $172 million, well down on the $383 million returned in the same period a year prior.

Bad weather cost Suncorp $280 million in a period it would normally expect around $100 million in claims.

Among Suncorp's insurance lines, home insurance performed best with 9% growth, while motor was up 6%.

Group banking profit offset some of the gloom, rising 10% to $323 million, before tax.

The company also upgraded synergies from the Promina acquisition to $325 million per year.

Full year pre-tax profit is expected to be 10-12%.

Suncorp expects full year pre-tax impact of the credit crunch to remain in the $10-15 million bracket forecast in October.

Suncorp shares were down 7.9% in Thursday's trading to close at $14.31.