Noble Group is being sued by one of its top shareholders in a fresh blow to the embattled commodities trader as it defaults on debt obligations.

Goldilocks Investment filed a lawsuit yesterday in the Singapore High Court against the company and executives, including founder Richard Elman, alleging the trader inflated profits to raise money, according to a copy of the writ of summons seen by Bloomberg.

Separately, S&P Global Ratings cut Noble's credit score to a level signifying default after it said the trader missed principal and interest payments on dollar-denominated bonds due yesterday.

Once Asia's largest commodity trader, Noble is teetering on the brink of collapse following a crisis that started three years ago when Iceberg Research began publishing critiques of its accounting. Executives led by chairman Paul Brough are now trying to push through a restructuring plan that will hand control to a group of senior creditors, but they are facing opposition from shareholders and some creditors.

"If anything, this will likely drag out the debt restructuring process and increases the uncertainty on the outcome," said credit analyst Ang Chung Yuh of iFast Corp. "It is not good news for Noble for sure."

The suit alleges management staff paid themselves inflated salaries, and then tried a cover-up when the accounts came under increased scrutiny, according to a copy of the case filed by Morgan Lewis Stamford and seen by Bloomberg. As well as Mr Elman, the defendants include Mr Brough, chief executive officer Will Randall and chief financial officer Paul Jackaman.

Noble declined to comment through an external media representative.

"We confirm that our client has commenced proceedings in the Singapore High Court," said Mr Daniel Chia, a Morgan Lewis Stamford lawyer acting for Goldilocks.

Goldilocks is seeking relief from Hong Kong-based Noble Group on behalf of shareholders, including about US$169 million (S$223 million) paid to executives between 2011 and last year, as well as any interest and damages assessed by the court, according to the lawsuit. Goldilocks also wants a declaration from the court that the defendants breached their fiduciary duties.

Goldilocks is seeking relief from Hong Kong-based Noble on behalf of shareholders, including about US$169 million (S$223 million) paid to executives between 2011 and last year, as well as any interest and damages assessed by the court, according to the lawsuit. The 72-page filing cites allegations made by long-time critic Iceberg. Goldilocks also wants a declaration from the court that the defendants breached their fiduciary duties.

Goldilocks began building up its equity holding in Noble last year, ploughing in funds even after the trader had faced criticism. In January, Goldilocks urged the Singapore regulator to probe Noble's actions, saying there were grounds for an investigation into the company, its directors and management. It has also been vocal in opposing the restructuring proposal.

The lawsuit may be another significant hurdle for the restructuring process, which needs approval from bond holders as well as shareholders.

BLOOMBERG