Willis Commercial Network plans to increase the amount of business traded by its intermediaries to £500m by the end of 2005, up from £150m last year.
The network allows small brokers to maintain independence, but Willis will provide information technology structures, agencies and products. The network is owned by Willis Commercial Risks.
The first broker to sign up was Northampton's CR King & Co in November 1998. Last month, Croydon-based Francis Townsend Hayward joined the network. However, Bishops in Kent left it on 31 March. The total number of commercial brokers in the network is now 50.
Willis Commercial Risks chief executive Hugh Warren said: "We have about 65 available marketing territories and we always thought that 50 was the key amount we would fill. We will probably recruit another five brokers this year."
He said that although intermediaries in the network can trade anywhere in the country, there are certain postal areas Willis is keen to attract. These include Bristol, Guildford, Southampton, Swindon, the City of London, the West End of London, Chelmsford and Colchester and Birmingham city centre.
In 2001, £150m of premium was traded in the network. An estimated £135m was placed with Norwich Union, Royal & SunAlliance, Zurich, AXA and Allianz Cornhill Regional.
Warren said Willis would help brokers in the network, which are General Insurance Standards Council-regulated and have an average premium of £5m, to acquire smaller intermediaries trading £2m or less. This would increase the amount brokers in the network trade by £350m over the next three years.