Auto and mortgage lender GMAC Financial Services said on Tuesday its quarterly net loss widened to $3.9 billion in the second quarter, from $2.5 billion a year ago, reflecting charges related to the company's incorporation and mortgage losses.

GMAC said its auto finance unit lost $727 million in the quarter, while its mortgage operations posted a $1.8 billion loss.

The quarter included a $1.2 billion charge related to GMAC's incorporation. GMAC converted in June from a partnership into a corporation in a move that could allow the company to sell shares to the public.

GMAC has received $12.5 billion in government aid since December, when it became a bank holding company, to combat mounting mortgage losses and falling vehicle sales.

(Reporting by Nick Zieminski, Editing by Maureen Bavdek)