US regulators on Wednesday filed civil charges against collapsed hedge fund Amaranth Advisors and its former star natural-gas trader Brian Hunter, alleging they attempted to manipulate prices of natural gas futures last year.

The Commodity Futures Trading Commission said Amaranth and Mr Hunter “intentionally and unlawfully attempted to manipulate the price of natural gas futures contracts” on the New York Mercantile Exchange on February 24 and on April 26 last year.