German carmakers Porsche and Volkswagen announced Friday shareholder meetings for December to approve a merger between the two - despite warnings of possible lawsuits and high tax bills, according to dpa. Under terms agreed two years ago, Volkswagen AG will takeover Porsche, but the families that own the Porsche sports car factories will become dominant shareholders. Porsche's earlier reverse takeover bid for the bigger VW, which started in 2007, failed in a credit crunch. Some investors hope to sue the merged company for massive damages over the losses Porsche sustained, and the group also faces an major tax bill on merger. Porsche SE said at its annual shareholder meeting in Stuttgart that an extraordinary meeting would be called in December. "Our clear, common goal is the merger," said Martin Winterkorn, who is chief executive officer of both Volkswagen and Porsche although the firms remain legally separate. "We are growing together." At Volkswagen's Wolfsburg main office, a spokesman confirmed Europe's biggest carmaker would also summon shareholders in December. Neither disclosed an exact date. The companies refuse to disclose if they have devised ways to avoid the liability issues. "How the issues will be dealt with, and when, can't be disclosed yet," said Porsche chief financial officer Hans Dieter Poetsch. Volkswagen meanwhile told workers to expect overtime and to cancel some of their summer holidays so that output from the main Wolfsburg factories can be kept up to meet the huge export demand. Labour leaders said the extra shifts in the third quarter of the year were being negotiated now. As a whole, the group's nine brands shipped 3.37 million cars in the first five months of this year, a group record and a gain of nearly 15 per cent from last year. Sales in China alone soared 18 per cent to 921,100 vehicles in the period.