Dr Jim Swire and other relatives are working with Gareth Peirce to compel the UK Government under human rights legislation to allow an inquiry into the tragedy that killed 270 people 21 years ago.

Ms Peirce’s clients include the Birmingham Six, the Guildford Four and the family of Jean Charles de Menezes.

Dr Swire, whose daughter Flora died in the bombing, said he was still waiting to hear from Gordon Brown after he and 10 other relatives delivered a letter to 10 Downing Street in October calling for a full public inquiry.

He wants the case to be taken in England as he says he has lost faith in the Scottish legal system.

“We are pestering him (Mr Brown) for a response,” said Dr Swire. “The next step will be a legal letter from Gareth Peirce explaining that they need to provide an inquiry under the European Convention on Human Rights (ECHR).

“There has been no public inquiry despite every Prime Minister in the past 21 years being asked for one. Lockerbie could have been prevented and we want to know why it wasn’t.”

Earlier this year Dr Swire received a letter from the Prime Minister saying he would not back an inquiry. The relatives believe that a public inquiry offers the last realistic hope of finding out how and why their loves ones perished.

Lawyers say that under Article 2 of the ECHR, which pertains to the right to life, there is also the right to an inquiry into how that life was taken.

“Although there was a Fatal Accident Inquiry in Dumfries, this was then undermined by new evidence including the break-in at Heathrow airport,” said Professor Robert Black, one of the architects of the original trial at Camp Zeist.

In a recent article in the London Review of Books, Ms Peirce wrote: “The devastation caused by the explosion of Pan Am Flight 103 over Lockerbie, at the cost of 270 lives, deserved an investigation of utter integrity. Article 2 of the European Convention on Human Rights demands no less.

Where there has been a death any inquiry must be independent, effective and subject to public scrutiny, to provide the basis for an attribution of responsibility and to initiate criminal proceedings where appropriate. But, in the absence of this, a number of the bereaved Lockerbie families have of necessity themselves become investigators, asking probing questions for two decades without receiving answers.”

The Scottish Government has said it would back an inquiry but that it requires UK jurisdiction.

The news came on the 21st anniversary of the bombing and follows reports that the health of the Libyan convicted of the bombing has deteriorated.

Abdelbaset Ali Mohmed al Megrahi, who has terminal prostate cancer, was granted early release in August as medical reports suggested he had less than three months to live. He was admitted to a medical centre on Saturday and a scan showed his condition was worsening.

The Scottish Criminal Cases Review Commission yesterday announced that in February it can release some of the material involved in its three-and-a-half-year investigation into the case, which led to it being referred back for a fresh appeal on six different grounds in June 2007.

A spokesman for Downing Street, said: “There will not be a public inquiry.”

Father Pat Keegans, the priest in Lockerbie at the time of the bombing, had been invited to address the memorial service at Arlington cemetery yesterday. However, Frank Duggan, president of group Pan Am 103, took offence at the extract published in yesterday’s Herald and stopped the address going ahead.