Any blow to confidence could be crucial for jittery brokers who are already nervous ...

Any blow to confidence could be crucial for jittery brokers who are already nervous about placing new long term risk with R&SA.

Many worry that if they do withdraw business from the troubled company, it could prompt a "run on the bank".

The Broker Network managing director Grant Ellis said: "It's quite an uphill struggle now to convince people they've got a viable business, though they may well have. We haven't started mass cancellation yet, but we're being quite circumspect about where business is placed."

The company's place in the bluechip index, updated on Wednesday, depends on its market capitalisation which is linked to its share price.

The company's results failed to impress investors last week, with a group operating result of £226m and a total dividend for the year of 6p. The stock remains stuck below 70p following the announcement.

One regional broker said that R&SA would be in "big trouble" if Standard & Poor's downgraded its A- rating.

A run on the bank could follow, he warned.

One senior broking figure agreed that R&SA needed to allay brokers' concerns, but said: "I can't see the FSA letting them go under."

Fitch last month downgraded the insurer to BBB+ from A- but Standard & Poor's maintained its A- rating after the financial results.

R&SA UK chief executive Duncan Boyle admitted he saw no immediate prospect of the company's share price improving, but was delighted by Standard & Poor's confidence. "This was always going to be the greatest stress point as to whether the ratings agencies would stay with us," he said. "We are going upwards from here on the capital front."

Standard & Poor's credit analyst Mark Button said the rating depended on the success of R&SA's £800m capital raising plan.