The poll results are preliminary and come during the fifth week of merger talks between the two German lenders. Employees have until May 3 to voice their opinion in the poll conducted by the works council representing the bank's headquarters.
Commerzbank declined to comment. The opposition at Commerzbank is fiercer than at Deutsche Bank, where a similar survey showed nearly 70 percent were against a tie-up. Unions have said that a merger could result in the loss of 30,000 jobs.
"Distance yourselves from the merger plans," Commerzbank's works council wrote in an open email to the bank's management board with the survey results. (Reporting by Tom Sims Editing by Tassilo Hummel and Michelle Martin.