Royal & SunAlliance (R&SA) has issued brokers with a harsh warning - if you haven't been a good business partner, don't come to us.
The insurer set out tough terms in its most recent broker briefing paper, after being inundated with new business inquiries.
The briefing said R&SA would not consider risks marketed at last renewal or risks presented less than five days before the target date.
It also listed almost 100 "unacceptable trades and occupations", including large US exposure, liability, aviation and motor fleet.
The briefing explained: "We will focus on those that experience has shown have real potential and eliminate those that analysis has shown as largely unproductive.
"To facilitate this, we are introducing measures to eliminate those unproductive enquiries."
Marketing and distribution director Brendan McManus said R&SA had received more new business inquiries than it could cope with since the World Trade Centre attacks.
"One of our smaller branches is averaging 500 more requests per week than it was getting before 11 September," he said."There's no way we've got the resources to deal with it."
He said R&SA would give priority to existing clients who had been loyal in the past and offered a spread of business.
"We haven't introduced a whole list of business we don't want to insure; we're helping brokers understand what will get our attention," he said.
"If people only want to put liability with us, it wouldn't be a high priority.
"If the business has been marketed every year, they're not the clients we're trying to attract.
"Clients that ask the broker to market every renewal won't stay with us and we can't develop a relationship."
McManus said other insurers had introduced similar strictures.
"We're all looking for that elusive client that will stay with you," he said.