Claims management specialist Albany ULR has won a bid to cover 150,000 private car policies for HSBC Select.
The company will provide claims management and uninsured loss recovery services for two years.
HSBC Select offers telephone and internet broking services to corporate clients that wish to offer their own customers or employees an insurance broking service without overheads or administrative problems.
The contract, which boosts Albany's policy base by 10%, comes after a strategic decision 18 months ago to provide only before-the-event legal expense insurance and services, rather than providing after-the-event.
Albany chief executive Bryan Irving said: "We wanted to position ourselves as insurer-friendly. We wanted to attract business from large broker groups."
The HSBC Select deal was a "milestone", he said.
"Our success in securing this prestigious contract provides us with a clear endorsement from one of the biggest names in financial services and supports our commitment to develop a wider array of products and services.
"We see ourselves very much as an outsource provider of solutions to the branded insurance schemes market," Irving said.
HSBC Select products director Paul Finigan said: "Our clients will receive a speedier and more efficient service and our relationship with Albany will enable us to extend our range of products and services."