Lockerbie families consider another appeal against al-Megrahi's conviction

"The intention of some members is to meet with lawyers in January and discuss the best options, the best way to get the truth," he said.

"It's a disgrace that we have to wait 25 years to get the truth that should be available from our governments."

The group will also consider whether an inquiry is the best route to get answers, although Dr Swire concedes that approach may ultimately fail.

He is part of another group pursuing a long-running petition at the Scottish Parliament which calls for the Scottish Government to open a full public inquiry into the conviction of Abdelbaset al-Megrahi.

Last December, Dr Swire said the family of the convicted bomber could be risking their lives if they raise the prospect of launching a fresh appeal against conviction, possibly leaving it to victims' families.

Dr Swire said new evidence needs to be investigated, including allegations surrounding a break-in at Heathrow Airport before the bombing of Pan Am flight 103, which killed 270 people in the air and on the ground.

"It's clear following the evidence and the behaviour of certain governments that Megrahi wasn't involved at all," he said.

The potential cost of a new appeal is not a major concern in the new discussion.

"That can be addressed with confidence," he said.

"There are so many lawyers and others who are aware that something is drastically wrong.

"There would be unstoppable momentum."

If successful, a new application to the SCCRC could start the third appeal into the conviction.

Megrahi lost his first appeal in 2002, one year after he was found guilty of mass murder and jailed for life.

The SCCRC recommended in 2007 that Megrahi should be granted a second appeal against his conviction.

He dropped his appeal two days before being released from prison in August 2009 on compassionate grounds.

Details of six grounds for referral to appeal were published last year.

Four of the reasons refer to undisclosed evidence from the Crown to Megrahi's defence team.

Those grounds cover evidence about a positive identification of Megrahi by Tony Gauci, a Maltese shopkeeper who said he sold clothes to a Libyan man.

The clothes were linked to a suitcase loaded on to the plane, which was then linked to the bomb and eventually to Megrahi.

The SCCRC raised concerns that evidence suggesting Mr Gauci had seen a magazine article linking Megrahi to the bomb was not passed to the defence.

Contradictions about the day Megrahi was said to have bought the clothes were also highlighted. The court was told the purchase was on December 7 but the SCCRC said Mr Gauci also thought it might have been November 29.

Also of concern to the SCCRC was undisclosed evidence about Mr Gauci's interest in rewards.

The commission said the defence should have been told that a substantial reward was on offer from the US government.

A fifth reason covered "secret" intelligence documents not seen by Megrahi's legal team while the sixth referred to new evidence on the date of clothes purchased in Malta.

Earlier this week, the top law officer in Scotland, Lord Advocate Frank Mulholland, announced that Libya has appointed two prosecutors to work on the investigation into the bombing.

He said it is a "very welcome development" which he hoped "will bear fruit and result in bringing others to justice".

Also this week, the former head of the FBI said he believes more people will be charged.

Robert Mueller, who finished a 12-year spell as FBI director in September, said progress has been made in the investigation since the Libyan revolution in 2011.

The Libyan justice minister said investigators from Britain and the US will be able to interview Abdullah Senussi, the Libyan intelligence chief at the time of the bombing.

Senussi was arrested after the fall of the Gaddafi regime and is awaiting trial for alleged crimes against humanity during his time in office.