* Opposition at Commerzbank stronger than at Deutsche
* Survey results are preliminary
* Survey taken during 5th week of merger talks
* Commerzbank declines to comment (Adds details from survey, background)
FRANKFURT, April 17 (Reuters) - About 83 percent of Commerzbank employees who took part in a staff survey are against a merger with Deutsche Bank, according to preliminary results of the poll seen by Reuters on Wednesday.
Germany's two largest banks said in March they were in talks to merge, a tie-up that unions have said could result in the loss of 30,000 jobs.
Opposition to the proposed deal is stronger at Commerzbank than Deutsche Bank, where a similar survey showed nearly 70 percent did not favour a tie-up.
"Distance yourselves from the merger plans," Commerzbank's works council wrote in an open email to the bank's management board with the results of the survey, taken during the fifth week of merger talks between the two banks.
Commerzbank declined to comment.
Employees' opinions count in Germany because workers make up half of companies' supervisory boards that usually are required to sign off on mergers. The strength of feeling among staff against the merger could also help labour to win concessions from management in exchange for their support.
The survey results are preliminary because Commerzbank employees have until May 3 to give their opinions in the poll conducted by the bank's headquarters staff works council.
Of 11,000 employees sent the survey, 5,500 had responded as of Wednesday morning, with many away for the Easter holiday. Of those who responded, 82.5 percent said the two banks should not merge, 13.7 percent that they should, and 3.8 percent had no opinion.
The potential merger with Deutsche Bank has prompted media speculation in Germany about boardroom rows at Commerzbank over the proposal. Last week, Commerzbank's supervisory board chairman Stefan Schmittmann dismissed reports of board dissatisfaction with CEO Martin Zielke as irresponsible and unfounded.
Zielke has already tried to win over employees.
Days after the talks were announced, Zielke promised the bank's employees a quick decision on whether to go forward with a merger, according to a memo seen by Reuters.
The Commerzbank works council has since written to the board members to protest against the merger, saying the idea lacked support among workers, customers and society.
Zielke has since met with staff to put the case for the deal.
Reporting by Tom Sims Editing by Tassilo Hummel/Michelle Martin/Jane Merriman