The Winter Review and Consultation report found the margin of spare generating capacity could be as low as 1.2% for this coming winter, compared to 4.1% last winter.
The report presents a review of the security of supply in gas and electricity for the last winter, launching an industry consultation on National Grid's forecasts for the coming winter, which will conclude in August.
Scottish Energy Minister Fergus Ewing said the situation shows 'complacency' by the UK Government, adding next year the margins 'could be under even greater pressure' if Longannet power station is forced to close prematurely.
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Mr Ewing said: "These figures show that the national grid is becoming even harder pressed to keep the lights on this winter.
"Thermal energy is a source of generation which has a significant impact on grid capacity margins and can enhance energy security.
"At a time when the UK Government is presiding over a period of extremely narrow generation capacity margins, it has chosen not to intervene regarding the unfair transmission charges which are threatening the future of thermal generation in Scotland.
"Given the need to address shrinking capacity margins it makes no sense to cancel planned onshore wind developments, as the UK government is doing through the removal of financial support. The situation of narrowing capacity margins will only be exacerbated if Longannet closes prematurely.
"It is vital, therefore, that all possible options for averting the premature closure of the Longannet site are explored, such as action to address discriminatory transmission charges."
The current transmission charging regime for Great Britain was introduced by the UK Government in 2005.
(LM)
