The makers of the timer used to explode the Lockerbie bomb will travel to Scotland following the revelation that their former employee planted vital evidence.

Edwin Bollier, whose now bankrupt company Mebo manufactured the timer switch that prosecutors used to implicate Libya, plans to visit Scotland with police forensics experts, following news that an engineer was asked to fabricate evidence.

Ulrich Lumpert, formerly an electronics engineer with Mebo AG, Zurich, has signed an affidavit admitting he committed perjury before the Scottish Court in the Netherlands.

In his affidavit he states that he stole a handmade sample of an "MST-13 Timer PC-board" from Mebo in Zurich and handed it over, on June 22 1989, to an "official person investigating the Lockerbie case."

He further states that the fragment of the timer, cut into two pieces for "supposedly forensic reasons," which was presented in court stemmed from the same piece.

He further states that when he became aware that this piece was used for an "intentional politically motivated criminal undertaking" he decided, out of fear for his life, to keep silent on the matter.

Mr Bollier has already spoken to prosecutors in Switzerland who will begin their investigation into charges of perjury next week.

The timer was used as a key part of the evidence against Abdelbaset Ali Mohmed al Megrahi, the Libyan convicted of the 1988 bombing which killed 270 people. The revelation will strengthen Megrahi's fresh appeal which was granted in June by the Scottish Criminal Case Review Commission.

Despite Megrahi's conviction, there have been persistent claims that Libya was not responsible, some evidence was rigged, and the finger of suspicion pointed elsewhere.

The commission rejected allegations that evidence had been falsified or "spirited away" by the investigating teams, but the affidavit by Mr Lumpert suggests otherwise.

Mr Bollier told The Herald last night: "We hope to go to Scotland with the police and forensics people from Switzerland to see the manipulated fragment. We have forwarded on the papers and affidavit to prosecutors here and they will also be passed to the lord Advocate in Scotland."

In 2001, Mr Bollier spent five days in the witness box at the Lockerbie trial at Camp Zeist in the Netherlands.

He told The Herald that the fragments he was shown at the trial were different to those originally shown to him. "The fragments kept changing," he said. "The procurator-fiscal showed me one fragment then the police showed me a fragment in two parts - one was green, one was brown.

"Later in the witness box I was shown a screen and the smaller piece was completely carbonised - you could not even see the colour. It had been manipulated, but when I tried to say that the judge cut me off."

Dr Hans Koechler, international UN observer at the Scottish Court in the Netherlands, has seen a copy of the affidavit made on July 18. He said: "The Scottish authorities are now obliged to investigate this situation. Not only has Mr Lumpert admitted to stealing a sample of the timer, but to the fact he gave it to an official and then lied in court."