Energy company EDF has told its workers that "uncertainties" remain about the impact independence would have on its operations.

In an email to its 15,000 UK staff, chief executive officer Vincent de Rivaz said the company was "not policy neutral" in the debate over Scotland's future and warned of the risks of leaving the union.

Employees with a vote face an "enormous responsibility" and the outcome "will affect" EDF Energy, he said.

"From the outset I have said that it is not my place to tell voters how they should vote," he wrote.

"But we are not policy neutral and it is my responsibility to defend the interests of our company."

EDF Energy employs 1,200 workers and runs two nuclear power stations - Hunterston and Torness - in Scotland which account for a third of total electricity generation capacity in the nation.

Mr de Rivaz said that both stations will "remain in Scotland whatever the outcome" but insisted key questions remain unanswered, including over regulation of the industry.

He also told staff there has been a failure to set out who would be responsible for long-term liabilities, such as paying for decommissioning as well as uncertainty over pensions, taxes, and currency.

"What is clear is that, beyond the primary reassurance about the ongoing operation of nuclear, the answers to these questions remain uncertain, depending on the outcome of the vote and any negotiations that may follow," he wrote.

"I am not complacent about these uncertainties and we will be ready from the day after the vote to be fully engaged in a constructive way to tackle all of them in the interests of our business, our customers and our people."

Mr de Rivaz said that even if Scotland backs independence, it is in EDF Energy's interest to remain a united company.

"I will do my utmost to ensure that EDF Energy remains a single, strong company which is well-equipped to address the new challenges we will face whatever the outcome," he added.

Gary Smith, GMB national officer for energy and utilities, claimed First Minister Alex Salmond was not being honest about nuclear liabilities.

He 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 lifetime 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.

"He also isn't being honest about nuclear liabilities and the costs associated with managing decommissioning and waste.

"What is the long-term plan for storing the waste from Dounreay and from the two operating nuclear power stations? There does need to be some clarity as to what will happen to Scottish nuclear waste and the huge implications the answer has for Scotland.

"We have also long argued that Scotland's energy reserves and resources are owned by organisations based outside these shores.

"The two nuclear power stations are owned by a French state company and other parts of Scotland's energy infrastructure have overseas owners.

"Most of the oil and gas is owned by US and multinationals from other nations. When it comes to energy we live in an inter-dependent world."