Brokers Prentis Donegan Partners and Price Forbes are to merge their wholesale broking and underwriting management businesses.
The merged organisation will trade and operate under the Price Forbes name.
Terms of the merger were not disclosed, but Price Forbes chairman Simon Fisher will be chairman of the enlarged company. Prentis Donegan chairman Michael Donegan will be chief executive of Price Forbes.
The merged company will have gross written premiums of about $585m (£321m), and a staff of 175.
Price Forbes said the merger would more than double the size of the group's wholesale presence in the Lloyd's, London and Bermuda markets. Price Forbes Group president and chief executive Jeremy Cooke said the merger was the first step in growing the group's global wholesale presence.