The justice secretary told parliament that assurances had been given by the Libyan government that Megrahi's return would be treated in a "low-key" manner.
Scottish ministers have maintained that the decision to release Megrahi on compassionate grounds - which has been strongly criticised by the US government - followed due process and was the right one.
Going on the attack in parliament, Scottish Labour leader Iain Gray demanded to know whether any pressure was put on Megrahi in his decision to drop the appeal against his conviction, ahead of the move to grant him early release.
"Last week, the Scottish Government made a wrong decision, in the wrong way, with the wrong consequences," said Mr Gray.
"The cabinet secretary has mishandled this whole affair from start to finish."
Scottish Tory leader Annabel Goldie said Mr MacAskill's decision was not made in the name of Scotland - and said Megrahi should have been allowed to live out his days in a safe house or hospice in Scotland, which she argued would have avoided Thursday's scenes in Libya.
Brian Taylor BBC Scotland Political Editor
Utterly unscientific, I know, but Nationalist MSPs seemed, if anything, more content after the exchanges than in advance.
So where next? Following this emergency session, there will be a full-scale debate in the Scottish Parliament next week, with a vote.
SNP government ministers are pre-empting opposition attacks by tabling a motion of their own, supporting Mr MacAskill's decision.
It may prove a little difficult for the opposition parties to agree a single, common line - particularly with Labour keen to attack the SNP while the Conservatives want to widen the criticism to include the Prime Minister.
He said the decision was based neither on political, diplomatic nor economic considerations, telling parliament: "It was my decision and my decision alone. I stand by it and I'll live by the consequences."
Mr MacAskill said the decision by Megrahi to drop his appeal was entirely his.
And he went on to describe the Tories' suggestion as "ludicrous".
Mr MacAskill said: "We took clear advice from the deputy chief constable of Strathclyde Police force - our largest police authority."
He said 48 officers would have been required to "simply to cope with him being in the house".
He said hospice residents who were looking for "dignity in their last few moments" would have been faced with a "travelling circus" if Megrahi had been admitted.
Not all Labour MSPs disagreed with Mr MacAskill's decision.
Malcolm Chisholm, a Labour MSP and former minister, told parliament: "Can I regret the politicisation of what is a quasi-judicial decision, and for my part commend the justice secretary for a courageous decision, which is entirely consistent with both the principles of Scots law and Christian morality, as evidenced by the widespread support of churches across Scotland."
'Out of order'
The Scottish National Party administration said Scotland had a strong relationship with the US, which did not always depend on the two countries coming to agreement.
US president Barack Obama has hit out at Mr MacAskill's decision, while FBI boss Robert Mueller said the move had made "a mockery of justice" and given "comfort to terrorists around the world".
However, Mr Mueller's claims have been dismissed by Prime Minister Gordon Brown and Labour former First Minister Henry McLeish, who said the intervention was "totally out of order" and "none of his business".
Meanwhile, in a move pre-empting the opposition parties, the Scottish Government will lead a full debate on the Lockerbie decision at Holyrood, when it returns from summer recess at the start of September.
The Scottish Parliament has only been recalled on two previous occasions in its 10-year history, which came following the deaths of former First Minister Donald Dewar in 2000 and the Queen Mother in 2002.
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