(CNN) -- Scottish First Minister Alex Salmond says he is concerned that a U.S. senator is trying to create a link between oil giant BP and the release of the convicted Lockerbie bomber.
"No one has produced any evidence of such a link because there is none," Salmond wrote Monday in a letter to U.S. Sen. Robert Menendez, who has been seeking answers about the release of Abdelbeset Ali Mohmed al Megrahi.
Salmond said he watched "with concern" as Mendendez, in an interview Friday on British television, made an "attempt to insinuate such a link." He said Menendez used as evidence a letter from the chair of the Libyan British Business Council to Scottish Justice Secretary Kenny MacAskill, who made the decision to free the bomber last year.
"You have this letter because the Scottish government published this last year as part of our comprehensive issue of documentation related to the decision," Salmond said. "That being the case, you must also have seen the reply from Mr. MacAskill, also published, which stated that his decisions would be 'based on judicial grounds alone and economic and political considerations have no part in the process.'"
Salmond added, "In order to avoid any suggestion of misrepresentation, I trust that you will include that fact in future references."
MacAskill released al Megrahi a year ago on compassionate grounds after doctors determined he was suffering from cancer and had three months to live. He has maintained the decision was his own. Despite the diagnosis, Al Megrahi remains alive.
Menendez plans to chair a U.S. Senate hearing in the coming months on the controversy surrounding al Megrahi's release. He and other senators from New York and New Jersey have repeatedly voiced suspicions that Scottish authorities released al Megrahi as part of a deal allowing oil giant BP to drill off the Libyan coast.
Scottish and British officials have declined invitations to testify at the hearing.
In his letter to Menendez on Monday, Salmond said his decision not to testify "was based on principle," because Scottish ministers are accountable only to the Scottish Parliament.
Under the Scotland Act 1998, Scotland has its own government that is responsible for most of the day-to-day issues there, including the justice system.
"It is difficult to envisage circumstances in which serving members of the U.S. government would agree to appear as witnesses in hearings or inquiries held by the legislature of another country, and there are many high-profile and indeed current examples of the U.S. government declining such invitations," he wrote.
Megrahi is the only person ever convicted in the bombing of Pan Am Flight 103, which exploded over the Scottish town of Lockerbie in December 1988, killing 270 people and 11 more on the ground.
Most of the dead were Americans. The flight had been heading to New York from Frankfurt, Germany, via London, England, when it blew up.
A special Scottish court in the Netherlands convicted Megrahi in 2001 and sentenced him to life in prison.
In 2007, Britain and Libya were negotiating a prisoner transfer agreement, and they sparred over whether to include al Megrahi. British officials and BP have said the oil company's interests -- mainly, seeking a huge deal to drill for oil in Libya -- were a consideration in those talks.
Al Megrahi was included in the transfer agreement, but he remained in a Scottish jail until August 2009, when MacAskill decided to free him on humanitarian grounds separate from the agreement.
Days after Britain and Libya concluded the transfer agreement last year, Libya and BP signed a deal for oil exploration. British and Libyan officials, and BP, have denied that al Megrahi's release played any role in the deal.
Salmond wrote Monday to Menendez that the Scottish government opposed the prisoner transfer agreement from the start, and he noted that both British and U.S. lawmakers at the time failed to heed Scottish warnings about the circumstances surrounding the deal.
He concludes by writing, "Please do not ascribe to the Scottish government economic or commercial motives for this decision when there is no evidence whatsoever for such a claim."