Claims teams will also get more training to catch out frauds, says chief executive Torrance.

Allianz will charge poor-performing brokers higher premiums in order to boost its motor business, the insurer said as it announced half-year results this week.

Andrew Torrance, Allianz’s chief executive, said: “We’ve increased our private car rates by five percentage points in the first half of the year but we’re also looking to take action in terms of looking at intermediaries whose performance is worse than average.

“We will be taking underwriting action and applying differential premium rate increases to poor-performing intermediary partners.”

Torrance said Allianz had no plans to withdraw capacity from the worst performers, but did not rule it out in the future.

Torrance said it was difficult to set an overall target for commission rates, adding that they should be decided on a case-by-case basis.

Allianz also revealed it is stepping up anti-fraud training among its underwriters and claims teams in an effort to thwart fraudulent claims.

Torrance said: “We seem to be getting more fraudulent claims now, where people with low-value motor cars report the car as stolen or it catches alight unexpectedly. These claims are sometimes driven by the fact that the car’s been into the garage and the garage has pronounced it requiring major repairs.”

Torrance said the insurer’s overall profit performance was adequate but largely driven by reserves from previous years, and the underlying profitability of the business was “unsatisfactory”.

Allianz’s first-half operating profit rose to £94m from £91.1m in the same period last year. Gross written premium income hit £802m, up 3.1% from £777.7m in the first half of 2007. Combined ratio hit 95.7%, up from 95.5% in the same period last year.

Commercial lines gross written premiums grew by 4.5% and the combined ratio at the end of the second quarter stood at 88.1%. But in retail, business grew by just 1% and the combined ratio reached 107.1% versus 99.6% last year.

Torrance said in the first quarter of this year that a 5% year-on-year increase in rates was required in 2008 in the insurer’s commercial property and liability books.

This week he said: “So far, that’s only being achieved in the fleet account. On average in the rest of the account, it’s between +1% and +2% in quarter two, which is better than we were getting in quarter one, but we’ve still got a way to get to +5%.

“The positive news is our retention rate has held up at 82% in the first half of the year for commercial lines.”

Torrance said the company was seeing a consistent, month-by-month rise in rates on renewals and, in June, it was in positive territory in each of its general commercial lines for the first time this year.

He added: “This is pleasing and shows the market is starting to move in the right direction, albeit more slowly than we would like.”