FRANKFURT - Volkswagen's  first-quarter earnings were weighed down by a loss on its stake in iconic sports car maker Porsche AG, VW's finance chief said on Thursday.

The Wolfsburg-based maker of the VW Golf accounts for its 49.9 percent stake in Porsche at equity, meaning it books the share of profits or losses at Porsche correlating to the size of its stakeholding.

The 3.9 billion euro ($5.2 billion) acquisition cost from December 2009 for the Porsche stake is subject to continual non-cash writedowns under IFRS regulations governing the allocation of the purchase price, called PPA effects.

These accounting charges more than offset VW's share of profit from Porsche, CFO Hans Dieter Poetsch told a conference call.

Volkswagen aims to subsume the sports car's majority parent Porsche SE in the course of next year, giving it full control over the iconic brand as well.

At the group level, improvements at all of Volkswagen's core brands drove the near-tripling of first-quarter operating profit, revealing in particular a sharp turnaround at the German carmaker's flagship VW brand.

(Reporting by Christiaan Hetzner)