An $18 billion merger deal between Willis Group Holdings and Towers Watson has been approved by shareholders in both firms — despite some opposition.

A spokesman for Willis, in a statement on preliminary results from the vote, said: “Shareholders of each company approved the proposals necessary to complete the merger-of-equals transaction.”

Willis chief executive officer Dominic Casserley added: “With the support of our shareholders, we are now focused on completing the transaction, successfully integrating the businesses and realising the combination’s full value-creation potential.”

Towers Watson chairman and CEO John Haley added: “We are confident that combining Towers Watson and Willis will accelerate both companies’ long-term strategies and create substantial incremental value for shareholders.” In a filing with the US Securities and Exchange Commission, Towers Watson said its shareholders approved the deal by a roughly three-to-one margin.

Last Friday’s votes on the deal, which Willis and Towers Watson said is expected to close “early in the new year”, overcame opposition on several shareholder fronts.

Proxy advisory firm Glass Lewis & Co said in a report at the start of December that the deal was “not structured in a manner which is fair or appropriately attractive for Towers Watson shareholders” and that they should reject the proposed $18 billion deal announced in June.

And some analysts also questioned whether the terms were fair to Towers Watson shareholders.

Towers Watson said in November it would raise the one-time cash dividend to $10 per share from the original $4.87 per share.

That appeared to convince the majority of shareholders to approve the deal, in which the combined company will be renamed Willis Towers Watson plc once complete.

The company’s shares will trade on the Nasdaq Stock Market.

In a recent SEC filing, the combination of the companies results in pro forma revenue of $5.56 billion and net income of $572.0 million for the nine-month period ended in September.

Pro forma revenue for 2014 was $7.3 billion with net income of $398 million.