Jim Swire, whose daughter Flora died in the bombing in December 1988, said the new Libyan regime wants nothing to do with links to Colonel Gaddafi.
He sounded the warning as it emerged that Tony Kelly, the lawyer who represented Abdelbaset al-Megrahi, is seeking a visa to visit family members in the capital, Tripoli.
Dr Swire, who was in the Scottish Parliament to hear MSPs keep alive a petition for an inquiry, said expert advice suggests the Megrahi family would be first in line to make any appeal, with relatives of the bombing "second on the list".
After Holyrood's Justice Committee met, he said: "The situation as regards the Megrahi family is that Tony Kelly, the lead figure for the defence of the Megrahi case, is seeking a visa to go to Libya for talks with the family.
"The situation in Libya is very difficult indeed. I can hardly see how the family will be able to make a decision whether to ask for a further appeal or not.
"It's hard to see where they would get any funding from to do it and, indeed, they might be risking their lives to do it because the subsequent regime following Colonel Gaddafi have been hell-bent on passing all blame to the Gaddafi regime. They have a position where they say that everything they did wrong was Gaddafi's fault, not Libya's fault.
"If the Megrahi family put their heads above the parapet and say 'although our dad was, before he died, a member of the Gadaffi regime, he wasn't guilty and we're going to contest the issue in Scotland again', it would be, to say the least, extremely unpopular.
"Having been to Libya fairly recently, where you can hear the stutter of AK-47s in the back streets at night still, if I were the Megrahi family I'd be very, very nervous about raising the issue of an appeal."
Mr Kelly confirmed he is seeking a visa to visit Megrahi's relatives but would not comment on the purpose of the visit and said any link to an appeal would be speculation.
"I'd arranged a visa but there were problems picking it up from the embassy, so I'm trying to secure another and visit Libya," he said.
MSPs of all parties on the committee agreed to keep the Justice for Megrahi petition open. It calls for the Scottish Government to open an independent inquiry into the conviction of Megrahi at a specially convened Scottish court in the Netherlands in 2001.
Megrahi, who had cancer, died in May this year. He was sentenced to life in prison for the bombing of a US airliner over Lockerbie in 1988, which claimed 270 lives.