Bristol & West, a subsidiary of the Bank of Ireland, is boosting its Independent Financial Adviser (IFA) business after acquiring Willis National for £40m.
The company will be merged with Moneyextra, which it bought last year.
Willis National was owned jointly by Willis Group Holdings and Abbey National and was created in 1997. The firm employs 300 staff in a network of 18 offices throughout the UK and 60% of its income derives from pension and corporate business.
Current Willis National chairman and chief executive Jeremy Budden will be standing down in the next six months.
The proposed transaction, which will be financed from the internal resources of Bank of Ireland Group, is expected to be completed by the end of July.
Joe Plumeri, chairman and chief executive of Willis Group, said: "As we focus increasingly on providing risk management services to the corporate sector, it is right that we reduce our presence in the IFA market."
Jeff Warren, chief executive of Bristol & West, said: "The purchase will complement our existing activities in this fast-growing market, accelerate the development of the Moneyextra proposition and add the important specialism of workplace advice."