A German bank staff union on Thursday called on Berlin to prevent UniCredit from buying Commerzbank, warning of massive job losses if the deal goes through.The warning by the DBV union comes days after the Italian bank announced it had acquired a 9% stake in Commerzbank and its leader said he would be keen to explore a merger.

UniCredit was able to buy 4.5% of Commerzbank from the German state because the government trusts the Italian bank, its CEO said in a newspaper interview, ruling out any "aggressive" moves such as an unsolicited buyout bid.