BP is being investigated by US regulators over alleged manipulation of the gas market, it has emerged.

The US Federal Energy Regulatory Commission (Ferc) notified BP of its preliminary conclusions relating to the alleged manipulation in November, a footnote to BP’s annual results, released yesterday, revealed.

Later that month the US Commodity Futures Trading Commission (CFTC) also served BP with a notice of intent to recommend charges over the same allegations. They relate to trades made by several BP entities that took place between October and November 2008 in Houston.

In a statement, BP said it had provided both agencies with a detailed response, saying that it “did not engage in any inappropriate or unlawful activity”. It added that it has fully co-operated with the investigations and that its trading and transport operations comply with the law.

In a separate case in 2006, BP paid $300m to settle charges that it had manipulated the propane market in the US.

The disclosure will not help BP rebuild its tarnished reputation following serious accidents in the US, the latest being last April’s disastrous Deepwater Horizon spill in the Gulf.

Separately, the administrator of BP’s $20bn (£12.3bn) Gulf spill compensation fund was accused last night by Mississippi’s attorney general, Jim Hood, of “sweeping deficiencies and violations of law”. He said that the courts needed to intervene to force BP to fulfil its legal obligations.

White House appointee Kenneth Feinberg took over the running of the fund from BP last summer. The statement filed with a federal court in Louisiana said: “Court intervention and action is needed to compel BP to cure its failure to provide a claims process that fulfills the requirements of the Oil Pollution Act of 1990, state law and prior public commitments of BP.”

The prospects of BP reaching a quick settlement over its dispute with Russian joint venture TNK-BP over the British company’s proposed new alliance with Kremlin-controlled rival Rosneft also dimmed last night. Rosneft’s chief financial officer, Peter O’Brien, said he “does not see” TNK-BP as a potential partner in the alliance, saying they did not have the right skills or personnel. TNK-BP has secured an injunction preventing BP from completing the share swap with Rosneft and freezing negotiations, claiming that it contravenes its shareholder agreement requiring BP to offer the joint venture first refusal on any business opportunities in Russia. The two sides are now preparing to begin arbitration proceedings.

At yesterday’s press conference, BP chief executive Bob Dudley said that it had always been BP’s intention to offer TNK-BP some sort of involvement in the Rosneft alliance, without giving details.