Two-thirds of the jobs at Commerzbank could disappear if UniCredit successfully carries out a hostile takeover of the German lender, a Commerzbank supervisory board member warned on Tuesday.

Stefan Wittmann, who is also a senior official at German trade union Verdi, told CNBC’s Annette Weisbach that “we certainly hope we can avoid” a hostile takeover by the Italian bank. Witmann said Commerzbank’s board had called on the German government to carry out an internal review of the possible takeover, which he hopes will give the bank a six-month period to take stock of the situation.

“But if it [a hostile takeover] is unavoidable, we think that two-thirds of jobs will disappear, that there will be another significant cut in the branches,” he said, according to a translation.

“We will see in particular that UniCredit does not want all Commerzbank customers at all, but that it focuses on the supposedly best customers, namely the wealthy customers,” he added.

Berlin, which was the largest shareholder of Commerzbank after it injected 18.2 billion euros ($20.2 billion) to rescue the lender during the 2008 financial crisis, is likely to play a key role in any potential merger between the banks.

“We are actually concerned with our economic and industrial responsibility. As far as the workforce is concerned, which trade unions are of course particularly focused on, they would always lose out in the merger, regardless of the point in time,” Wittmann said. The bank has yet to respond to a request for comment on Wittmann’s statements.

UniCredit announced Monday it had increased its stake in the German lender to around 21% and submitted a request to boost that holding to up to 29.9%, signaling a takeover bid might be in the cards. Earlier this month, the Italian bank took a 9% stake in Commerzbank, confirming that half of this shareholding was acquired from the German government.

UniCredit believes substantial value can be unlocked within Commerzbank, Germany’s second-largest lender, but it said that further action is required for that value to be “crystalized.”

German Chancellor Olaf Scholz criticized UniCredit’s move on Monday, saying, “unfriendly attacks, hostile takeovers are not a good thing for banks and that is why the German government has clearly positioned itself in this direction,” Reuters reported.

Commerzbank’s supervisory board is due to meet this week to discuss UniCredit’s stake, people familiar with the matter who asked to remain anonymous previously told CNBC.

Wittmann said the mood is currently “very tense” within the company, adding that the bank was surprised by UniCredit’s announcement on Monday, which he described as a “180 degree-turn within 48 hours.”

“[UniCredit CEO Andrea Orcel] last spoke on Friday that he wanted a friendly takeover in agreement with all stakeholders and politicians. And yesterday we were surprised by his hostile takeover attempt. That doesn’t add up,” Wittmann said.

The supervisory board member explained that the two main reasons to regard a potential merger in a critical light are the lack of a banking union in Europe, and the fact that UniCredit has “absorbed itself with Italian government bonds in recent years.”

He questioned what might happen should geopolitical tensions or “upheavals” impact UniCredit’s availability of capital to finance Commerzbank’s industry.

In response to the 2008 financial crisis, the European Commission announced plans to create a banking union to improve the regulation and supervision of banks across the region.

Economist and former European Central Bank Governor Mario Draghi flagged in a recent report that banks in Europe face regulatory hurdles which “constrain their capacity to lend,” also citing the “incomplete” banking union as one factor that impacts competitiveness for the region’s banks.

“We have always spoken out, including as employee representatives on the Supervisory Board, that there can and should be mergers at [a] European level, but only when the banking union is in place. And that is just our second point of criticism, that we say: create the rules of the game and the guardrails first, and then do it sensibly when it is clear which playing field we are on,” Wittmann said.