Willis Group is set to acquire PMI Heath Group (PMIHG) in a bid to expand its UK employee benefits and healthcare business.
The global risk advisory, re/insurance broking, and human capital and benefits firm said the deal would "significantly raise" its presence in the UK market and would add greater depth and range to its product offering and skills base.
The move comes just days after Willis announced it would merge with Towers Watson in an $18bn (£11.4bn) deal to form Willis Towers Watson.
PMIHG was established in 1986 and is the UK's largest independent provider of employee healthcare and risk management services. It offers a range of health and protection insurance, including services targeting absence management and occupational health.
Willis said it would be able to draw on the client-facing infrastructure and marketing expertise of PMIHG - noting existing clients at both businesses will benefit from access to a wider range of services and products.
Nicolas Aubert chief executive of Willis GB explained: "This deal is a major step forward for our human capital and benefits business, and offers strong synergies and future strategic opportunities.
"Both Willis Employee Benefits and PMI Health Group are recognised for their expertise and outstanding client service, and uniting these two wholly complementary businesses will enhance our competitive edge further."
Tony Powis chief executive Willis Employee Benefits added: "Our combined team will provide the scale, technology and expertise to deliver innovative and compelling value propositions.
"Organisations of all sizes are struggling to manage their employee risks such as absenteeism and presenteeism, and we are determined to shake this market up through innovative propositions."
Matthew Baldwin chief executive PMI Health Group said: "Joining with Willis will bring significant strategic opportunities and enable the PMI Health Group team and proposition to be an integral part of a growing, exciting and international business to service our clients."
The transaction is subject to regulatory approval and is expected to close in the third quarter of this year.
The terms of the transaction were not disclosed. After completion, PMIHG will use the Willis brand and maintain its operations at its current base in Wincham, Cheshire.