Shareholders of Willis Group Holdings and Towers Watson have voted in favour of their $US18 billion ($25 billion) “merger of equals”.

The new entity will be known as Willis Towers Watson.

The transaction is expected to close “very early in the new year”, subject to regulatory approvals.

Towers Watson CEO John Haley has thanked shareholders for their support.

“We are confident combining Towers Watson and Willis will accelerate both companies’ long-term strategies and create substantial incremental value for shareholders,” he said.

“We look forward to working with Willis to successfully complete the transaction and realise the full benefits of the merger for all of our stakeholders.”

Willis CEO Dominic Casserley says the immediate priority is “successfully integrating the businesses and realising the combination’s full value-creation potential”. 

“These efforts are well under way and we expect they will create substantial incremental shareholder value through revenue, cashflow and [earnings] growth superior to what either company could achieve independently,” he said.

Willis is listed on the New York Stock Exchange and Towers Watson is listed on the NASDAQ exchange. The combined entity will trade on the NASDAQ.

Willis Australasia Chairman and CEO Tony Barber was not available when insuranceNEWS.com.au sought comment.