BP signed an exploration agreement with Libya in May 2007, the same month Britain and Libya signed a memorandum of understanding that led to al-Megrahi's release.

But the company said on Thursday that it had not been involved in discussions regarding the release of al-Megrahi.

"The decision to release al-Megrahi in August 2009 was taken by the Scottish government. BP was not involved in any such discussions about the release of al-Megrahi," the statement said.

"BP told the UK government that we were concerned about the slow progress that was being made in concluding a prisoner transfer agreement with Libya.
 
"We were aware that this could have a negative impact on UK commercial interests, including the ratification by the Libyan government of BP's exploration agreement."

Senators' action

Hillary Clinton, the US secretary of state, said on Wednesday she would look into a request by four US senators to investigate BP's role in the al-Megrahi case.

The senators' action follows admission by Karol Sikora, a British cancer expert, to a newspaper earlier this week that al-Megrahi's survival past a three-month prognosis was "embarrassing".

Charles Schumer, senator from New York, said the evidence indicating BP had been involved was circumstantial - "but very strongly circumstantial".

"The bottom line is simple, if it walks like a duck and quacks like a duck then it just might be a corrupt deal between BP, the British government and Libya," he said.

"If BP is truly dealing in good faith and has nothing to hide it should co-operate with such an investigation."

The four Democrats said they were concerned that BP may have put profits ahead of justice in al-Megrahi's case, given the energy firm's current handling of the Gulf of Mexico oil spill.

"If BP is found to have gained access to Libyan oil reserves by using a mass murderer as a bargaining chip, then make no mistake any money it makes off of that oil is blood money, pure and simple," Robert Menendez, another senator, said.