A string of high profile British witnesses who refused to testify at a US Senate hearing into the release of the Lockerbie bomber are facing accusations of "stonewalling".
The US Senate Foreign Relations Committee has postponed Thursday's planned hearing after key witnesses including former Justice Secretary Jack Straw, Scottish Justice Secretary Kenny MacAskill and First Minister Alex Salmond turned down requests to attend.
Senator Robert Menendez, a Democrat who was due to chair the hearing, said "no witness of consequence has the courage" to step up and clear the air but insisted it will be held "in the near future".
He said: "It is utterly disappointing and I think pretty outrageous that none of these key witnesses will cooperate with our request to answer questions before the Senate Foreign Relations Committee. They have stonewalled."
The committee is investigating whether BP lobbied for Abdelbaset al Megrahi's release to help get a 900 million US dollar exploration agreement with Libya off the ground.
BP acknowledged it urged the British government to sign a prisoner transfer agreement with Libya, but stressed it did not specify his case.
Mr Menendez also attacked outgoing BP boss Tony Hayward for refusing to testify, saying: "It is apparently more important to BP and Mr Hayward to focus on his multi-million dollar golden parachute than to help answer serious lingering questions about whether the company advocated trading blood for oil."
Megrahi is the only person convicted of the 1988 bombing in which 270 people were killed. He was released on compassionate grounds last July after medical evidence indicated he only had three months live.
Calls for the decision to release Megrahi to be re-examined grew in volume in the wake of the Gulf of Mexico oil spill and revelations that BP lobbied for the PTA, amid concern that ditching it could damage an exploration deal it signed in Libya.
Foreign Secretary William Hague described Megrahi's release as "wrong and misguided" at the weekend.