The Libyan convicted of the Lockerbie bombing has formally dropped his second appeal against his conviction for the attack that killed 270 people.

Abdelbaset Ali Mohmed Al Megrahi, who is serving a 27-year sentence in HMP Greenock, applied to abandon the appeal last week - a procedure that was accepted yesterday by three judges at the Court of Criminal Appeal in Edinburgh.

Megrahi's defence team revealed that he made the decision to drop the case because he believed it would speed up the decision to allow him to return to Libya.

The Herald understands that Kenny MacAskill, the Justice Secretary, will allow Megrahi to return to Tripoli later this week on compassionate grounds. Ramadan begins on Friday and there is concern that he would not survive the strict fasting regime involved while in prison.

Seven senior US Senators yesterday wrote to the Justice Secretary to oppose such a move. They include leading Democrats John Kerry and Ted Kennedy.

However, a Libyan judge, who was in court yesterday as an "observer" to the hearing, said he should be allowed to return home to his family.

Honorary Justice Hamdi Fannoush said outside the courtroom that dropping the case was "not in the interests of justice".

Mr Fannoush said: "People want to know what happened but this closes the door on that opportunity.

"Megrahi wanted to clear his name in court but after trying every possible way of getting home to see his family, he felt forced to make this sacrifice.

"In Libya everyone is talking about this. They believe he is innocent and cannot understand why he is still not home when he is so ill. Judicially nothing more can be done now other than a public inquiry."

Maggie Scott, QC, Megrahi's advocate, told the court yesterday: "His absolute priority in the little time he has left is to spend it with his family in his homeland."

Ms Scott also told the court that her client believed dropping his appeal would speed up Mr MacAskill's decision on whether he should be freed or transferred to Libya.

Ms Scott added: "It's the appellant's belief that instructions to abandon his appeal will assist in the early determination of these applications."

She said the case met the guidelines for compassionate release and that "serious" health complications were "certain to arrive" in the very near future. She told the court that reports from three medical experts confirmed the grave and progressive nature of his illness.

She said he was now very weak, suffering severe pain, and in "great distress".

The Libyan government applied in May for Megrahi to be transferred home to serve the rest of his sentence there. However, such a move would be subject to judicial review and such opposition could have delayed a transfer for months.

Last month, Megrahi put in a separate request to the Scottish Government to be released on compassionate grounds, a move that could have been granted even if the appeal had continued.

Mr MacAskill has said he will announce his decision by the end of the month.

The court heard that a separate appeal by the Crown against the length of Megrahi's sentence was still outstanding. Such a "live" proceeding could prevent prisoner transfer but not compassionate release, which is judged on different grounds.

Lord Hamilton, Scotland's most senior judge who was sitting with Lord Eassie and Lady Paton, said it was "of the utmost importance" that the Lord Advocate Elish Angiolini makes an early decision on whether she intends to insist upon the appeal.

The judge said the court urged her to reach a decision on that matter without undue delay. If she has not dropped the appeal against the length of sentence there will be another procedural hearing in three weeks. Ronnie Clancy, QC for the Crown, said she had to consider the public interest.

The Rev John Mosey, whose daughter Helga, 19, died in the bombing, said the outcome was "more or less what we expected". He went on: "It's a sad day really. It's the worst possible decision for the families because we lose the opportunity to hear evidence that the Scottish Criminal Cases Review Commission thought was worth putting forward."

Mr Mosey said none of the big questions about Lockerbie had been answered.

"We are back where we started 21 years ago, asking for a wide-reaching independent inquiry into all aspects of this disaster," he said.

The Scottish Government made no comment on the outcome of the hearing.

A spokeswoman said: "This appeal has always been a matter for him, the courts, and his legal team."

Christine Grahame, a backbench SNP MSP who has visited Megrahi in prison, said outside court it was "extraordinary" that the Crown had not dropped its own appeal against Megrahi's sentence.

"The Crown was not prepared today to say whether they would drop their appeal." she said. "We had the extraordinary thing of the Crown saying they'd not seen the medical evidence."

She went on: "They have known this was coming before the court and I hope that within the next 24 hours they lodge something dropping their appeal."