Relatives of the British victims of the Lockerbie bombing have called for an independent inquiry into the atrocity.
The 1988 bombing killed 270 people
The appeal comes exactly 15 years after the tragedy, which killed 259 people on the Pan Am flight and 11 residents in the Scottish town.
Libyan Abdelbaset Ali Mohammed Al Megrahi was jailed for life after being found guilty of the bombing.
The pressure group UK Families Flight 103 said it welcomed Libya's recent decision to give up its weapons of mass destruction, but still sought a "just resolution" to the Lockerbie bombing.
Group secretary Pamela Dix, who lost her brother Peter in the bombing, told BBC News the most fundamental questions remained unanswered.
UK Families Flight 103 was determined to find answers "partly to prevent it from happening to other people, partly because we owe it to those who died to establish the whole truth", she went on.
"With the re-establishment of proper diplomatic relations with Libya... it may be that the door will open a little further and more information might emerge about what happened at Lockerbie."
Ms Dix said the UK Government had already shown "a certain amount of imagination" towards Lockerbie, above all by successfully negotiating so a criminal trial could be held in 2001.
"But unfortunately the trial has left many questions unanswered.
Megrahi's sentence is to be challenged
"Really it was not a forum to ask the big open-ended questions about Lockerbie, about why and how it happened, what the motivation for it was, who was behind it and why it was not prevented.
"Those extremely important questions have never been given a forum to be asked in."
Jim Swire, whose daughter died in the bombing, said the failure to act on warnings of a possible attack must be addressed.
"That inactivity and incompetence resulted in 270 innocent deaths," said Mr Swire.
"I think it's a rather more important reason for an independent inquiry into why Britain failed in her duty of protection of those innocent people than is the case for almost any other catastrophe that has been greeted with inquiries since Lockerbie happened."
Russell Brown, the Labour MP for Dumfries, said he had been in contact with Foreign Office Minister Baroness Symons about the families' concerns.
Mr Brown said: "Her responsibility does cover north Africa and Libya, so I am quite keen, if it is the wishes of the other UK families, to meet with Baroness Symons to raise some of these issues."
The special trial in the Netherlands ended with Al Megrahi, a former Libyan intelligence agent, being jailed for life.
He is serving his sentence at Barlinnie Prison in Glasgow and was last month told by three Scottish judges that he must spend at least 27 years in jail before being considered for parole.
On Thursday, Lord Advocate Colin Boyd QC, Scotland's senior law officer,
announced he would challenge the sentence on the grounds that it was unduly
The trial was among a series of moves helping to rehabilitate Libya's international reputation, which culminated in the announcement two days ago on weapons of mass destruction.
Libya's decision, which followed nine months of secret talks with the West, has received international praise.
Deputy Prime Minister John Prescott told BBC's Breakfast with Frost it was "a diplomatic coup".
He added: "There's an awful lot of people, many thousands, who are better off."
A spokesman for UK Families Flight 103 said: "We welcome Libya's stated intention to
abandon the creation of weapons of mass destruction and are pleased at the
British Government's attempts to find a peaceful solution to this issue.
"Throughout the 1990s and beyond we have encouraged dialogue between our countries, even when there was no political will for such negotiations."
However, according to a report in the Sunday Telegraph newspaper, Libyan leader Colonel Muammar Gaddafi only agreed to the deal because Britain and the United States had intercepted a shipment of suspected banned weapons.
A separate report in the Observer says Libya has provided detailed intelligence on hundreds of Islamic extremists, including al-Qaeda.
Meanwhile senior Libyan officials have already met the head of the UN's nuclear agency to discuss the elimination of Tripoli's weapons of mass destruction programme.