Suncorp has improved its forecast merger savings but downgraded its insurance trading ratio due to increased weather-related claims.

CEO John Mulcahy told an investor briefing on Friday the company has lifted its annual synergies target by 44% to $325 million following last year's $7.9 billion Promina merger. One-off implementation costs are up 6% to $375 million.

Suncorp has also reduced its exposure to natural catastrophes in the wake of a $280 million bill from weather-related claims in the second half of last year.

The company has spent $15.2 million on a retention buydown program providing protection against hail, storm and bushfire to June 30. The reinsurance halves Suncorp's maximum event retention to $100 million, dropping to $50 million for a further loss.

Mr Mulcahy expects rates to rise as a result of increased claims costs. "I would expect there would be premium increases across personal lines portfolios going forward," he said.

Suncorp's 2007/08 insurance trading ratio has been revised to 9%-12% from 13%-16%.