Royal & SunAlliance (R&SA) will save a "seven figure sum" by closing eight of its offices, corporate business director Brendan McManus said.
McManus said the offices ranged in size from around 35 staff in Leicester to 3 staff in some of the Scottish offices.
"We want to create more critical mass in the centres we've got by having the right efficiencies and you can only do that with centres with more people in them," he said.
The closed centres handled "mid-market business" with more than £1m turnover.
McManus said he expected some brokers would initially complain of deteriorating service.
"But, if anything, it will improve the level of service we're giving them," he said.
"Our key account managers will be working from home and they'll be out on the road developing relationships with brokers."