EDF Energy chief executive Vincent de Rivaz has warned that a vote of independence for Scotland would lead to a massive uncertainty for the energy sector.
de Rivaz accused Scottish National Party leader Alex Salmond of failing to answer questions regarding basic issues such as nuclear waste.
In an email sent to the company's 15,000 staff, of whom 1,200 are working in Scotland, the chief executive said that people voting for the referendum on Thursday had a huge responsibility and the outcome "will affect EDF Energy and its employees".
de Rivaz sent the email as he had to "defend the interests of our company" although it was not really his place "to tell voters how they should vote".
According to a report by The Telegraph, in the last four months, de Rivaz met Salmond twice.
While the chief executive had been able to secure assurances that the company's two nuclear plants would stay operatinal in Scotland, there were several other core questions that were not answered.
These issues included: how an independent Scotland would regulate its nuclear plants and the energy sector; how nuclear waste disposed by the Scottish plants would be handled; the impact of fiscal policies on the sector; and if there would be a single electricity wholesale market across Great Britain following secession.
EDF's 1,200 employees in Scotland work at its nuclear plants and an engineering centre in East Kilbride; the company also has around 500 contractors.
EDF's two nuclear power plants, Hunterston and Torness, cater to 46% of the power requirements of Scotland.
Although Salmond had vowed to turn Scotland nuclear free, he had assured EDF that the life of the two plants would be extended.
Meanwhile, GMB, the union for energy workers, says there is a need for some clarity on what will happen to Scottish nuclear waste and the huge implications the answer will have on Scotland.
GMB national secretary for energy and utilities Gary Smith said: "Alex Salmond has waxed lyrical about Scotland being the Saudi Arabia of renewables and being anti-nuclear.
"The truth is that whilst banging on about renewables and being anti-nuclear the SNP Government has been agreeing life-time extensions for nuclear plants. This is because Scotland needs nuclear.
"Power from the two Scottish nuclear power stations can meet nearly 50% of Scotland's electricity demand. Alex Salmond hasn't been candid about this fact."
Image: Torness nuclear power plant is operated by EDF Energy in Scotland. Photo: courtesy of EDF Energy.