Securities firm MF Global Holdings Ltd. is seeking bankruptcy protection one week after reporting its biggest ever quarterly loss and having its credit downgraded to junk status.

Fitch downgrades MF Global Holdings to junk

The company, run by former New Jersey Governor and Goldman Sachs head Jon Corzine, was downgraded by debt-rating agencies concerned about its big bets on European debt. It appears to be the first big U.S. casualty of Europe’s debt crisis.

MF Global filed its petition with the U.S. Bankruptcy Court for the Southern District of New York. It says it has assets of US$100 million to US$500 million and liabilities of US$10 million to US$50 million.