A UK public inquiry should be held into the release of the Lockerbie bomber, according to a backbench Tory MP.
Daniel Kawczynski, who chairs the Westminster all-party group on Libya, spoke out on Monday, calling on Scottish Justice Secretary Kenny MacAskill to apologise for the "huge error" in releasing Abdelbaset al-Megrahi almost a year ago.
It came as David Cameron flew into the US for his first visit since taking office. The Prime Minister is expecting to face criticism from American politicians over claims that BP lobbied for the release of Megrahi to secure an oil deal.
Mr MacAskill has already said he would be prepared to assist any inquiry held into circumstances surrounding Megrahi's release.
But Mr Kawcynski, the MP for Shrewsbury and Atcham, told Radio Scotland: "Clearly Mr MacAskill has made a huge error which has impacted on British foreign policy.
"So far, I haven't heard any explanation or apology from Mr MacAskill and it's very daunting for relatives of those who have died when ministers make decisions which turn out to be flawed, then they're not prepared to account for themselves and not even prepared to apologise.
"I would like to take this opportunity of asking Mr MacAskill to make an urgent statement and an apology for the gross error that he has made."
Mr Kawczynski said the "national Parliament" at Westminster would not be able to hold Mr MacAskill to account for the decision, adding: "That's why I think the only way to do it is to have a national public inquiry."
- Lockerbie bomber celebrates 58th birthday
- Lockerbie bomber's life expectancy under scrutiny
- US senators in protest letter over Lockerbie bomber's release
- Clinton to examine senators' claims over BP link to Lockerbie bomber
- Lockerbie doctor speaks out over Megrahi comments
Four US Democrat senators last week asked Britain to investigate the release of Megrahi, who has terminal cancer. They want an inquiry to examine claims that oil giant BP lobbied for his release to smooth an exploration deal with Libya. An influential senate committee is also to examine the case.
However, the Scottish Government has denied the claims, insisting Megrahi was released purely on compassionate grounds. He was freed in August last year after medical advice indicated he had less than three months to live, but he has now survived for almost a year.
A Scottish Government spokesman said the issues being raised in the US refer to the Prisoner Transfer Agreement negotiated by the governments of the UK and Libya, not the compassionate release decision.
He said BP made no representations to the Scottish Government, which had opposed the PTA negotiated between the UK and Libyan Governments.
A spokesman for First Minister Alex Salmond said: "If the US Senate wants to get the truth about the 'deal in the desert' by the UK and Libyan governments in 2007, they should call Tony Blair to give evidence.
"Blair was its architect - he would be the one who knows about an oil deal.
"Kenny MacAskill rejected Libya's prisoner transfer application for Al Megrahi, and he based his decisions on both the PTA and the compassionate release application on strict justice criteria."
Megrahi is the only man to have been convicted of the Lockerbie atrocity, which saw 270 people killed in the bombing of Pan Am Flight 103 on December 21 1988.
His release from Greenock Prison was met with anger, especially among victims' relatives and politicians in the US.