Political storm after bomber freed

Opposition parties said that ministers had "serious questions" to answer after Libyan leader Colonel Muammar Gaddafi's son, Saif, claimed that the decision to free Megrahi was tied to a trade agreement.

Business Secretary Lord Mandelson dismissed suggestions of a deal as "offensive", insisting the release of the terminally ill Megrahi on compassionate grounds was purely a matter for the Scottish government.

However Libyan television has showed pictures of Col Gaddafi himself meeting Megrahi and praising "my friend" Gordon Brown, the Queen, Prince Andrew and the British Government for their part in securing his freedom.

His appearance is further evidence that the unpredictable Libyan leader is prepared to defy calls by Mr Brown and US President Barack Obama for Megrahi's return to be handled in a low-key fashion.

Downing St has released the text of Mr Brown's letter to Col Gaddafi ahead of Megrahi's arrival. In it the Prime Minister said: "A high-profile return would cause further unnecessary pain for the families of the Lockerbie victims. It would also undermine Libya's growing international reputation."

Shadow foreign minister David Lidington said it was essential that Mr Brown himself answered the questions as to whether British ministers had at any time suggested or requested that Megrahi should be released or transferred to a Libyan jail.

"I think there are some serious questions to be asked," he told the BBC Radio 4 Today programme. "It is very important, I think, for the reputation of our institutions of justice that it is made clear beyond any doubt that this was not connected with some political trade."

The speculation about the role played by London has been fuelled by the disclosure that Lord Mandelson met Saif al Islam Gaddafi earlier this month while holidaying on the Greek island of Corfu.

But as he left St Mary's Hospital in London after a routine prostate operation, Lord Mandelson flatly denied that there had been any deal. "It's not only completely wrong to make such a suggestion it's also quite offensive," he said.