The man convicted of the Lockerbie bombing has released a dossier of legal papers which he claims are proof he was wrongly convicted of the worst terrorist attack on British soil.

The documents, published online today by Abdel Basset al-Megrahi, show that serious doubts about the reliability of the key witness at his trial were raised independently by Scotland's official body, which investigates suspected miscarriages of justice.

The dossier demonstrates that the Scottish Criminal Cases Review Commission (SCCRC) sent Megrahi's case back to the court of appeal in 2007, after deciding that the judges who convicted him had made a series of errors about the evidence of a Maltese shopkeeper, Tony Gauci – the only witness to link the Libyan to the alleged plot.

According to the commission, those mistakes were significant enough to raise substantial doubts about the safety of Megrahi's conviction of killing 270 people in the Lockerbie bombing on 21 December 1988.

The crucial mistake, the SCCRC said, was believing prosecution claims that Megrahi had bought clothes at Gauci's shop on 7 December 1988, allegedly used later in the suitcase bomb. This evidence was "unreasonable", the SCCRC said, and was alone grounds for belief that Megrahi was wrongly convicted.

The commission said that evidence available at the trial, including the weather and the time Christmas lights were switched on near Gauci's shop, suggested that the clothes were actually bought on 23 November 1988 – when Megrahi was not in Malta.

The 298-page dossier, published on a website specially set up for the purpose, is the convicted bomber's attempt to prove his innocence after his controversial release from Greenock prison on compassionate grounds last month. Megrahi is in the terminal stages of prostate cancer, and Scottish ministers believe he has less than three months to live.

The papers were used for the first two stages of his appeal earlier this year, but Megrahi abandoned the appeal two days before he was freed and before the appeal court could give its judgement on the first grounds for appeal.

When Megrahi confirmed the case was being dropped his lawyers told the appeal court that he believed this would speed up his release, fuelling claims – later denied by Megrahi – that a deal was struck to prevent embarrassing evidence about his conviction emerging in court.

In a statement released today by his solicitors, Megrahi said: "I have returned to Tripoli with my unjust conviction still in place. As a result of the abandonment of my appeal I have been deprived of the opportunity to clear my name through the formal appeal process. I have vowed to continue my attempts to clear my name.

"I will do everything in my power to persuade the public, and in particular the Scottish public, of my innocence."

In a reference to the many US relatives and senior figures in the US government who were furious at his release, including the secretary of state, Hillary Clinton, he said he hoped the papers would "assist in the understanding of my case, especially for those who have been most profoundly affected by it".

According to the dossier, the commission believed that the three judges who jailed Megrahi after an unprecedented trial in Holland in January 2001 had unreasonably dismissed a number of contradictions and ambiguities in Gauci's interviews with police and in court.

Megrahi's lawyers said Gauci was interviewed 23 times by Scottish police, and an undisclosed number of times by FBI and CIA investigators. He first appeared to identify Megrahi 27 months after the date of purchase of the clothes, while it took 12 years for the trial to take place. His lawyers are expected to allege next week that Gauci received a $2m reward after Megrahi's conviction.

The SCCRC said that Gauci's interviews and his evidence in court showed that he: was unable to identify the date the clothes were bought, and frequently said it may have been November or December; was confused about the date the Christmas lights went up; repeatedly told police he could not remember the exact time or day.

The commission concluded that the judges reached an unreasonable verdict based on unreliable evidence, Megrahi's appeal papers state. Megrahi's lawyers added that the verdict "consists of defective reasoning or self-misdirection in a number of respects".

His documents also reveal detailed challenges to key aspects of the bomb plot as described by prosecutors. There was no proof that the suitcase was put on board a feeder flight at Luqa airport in Malta which went to Frankfurt airport on 21 December. There was also no evidence to prove that Megrahi had been involved in the plot, and the dossier claims that the judges had unfairly rejected defence evidence at the trial that pointed towards a different culprit: the Iranian-funded Popular Front for the Liberation of Palestine-General Command.