The Scottish Executive has the power to stop nuclear power stations being built whatever the Westminster government decides, the first minister has said.
Two nuclear power stations in Scotland are near the end of their lives
Energy policy is a reserved matter on which Holyrood does not legislate.
However, it emerged that Jack McConnell was referring to a little-known clause in the 1989 Electricity Act.
The first minister also said that there would be no new nuclear power stations in Scotland until the issue of managing radioactive waste was resolved.
Mr McConnell has previously said that Scottish ministers will aim to block any attempt to build a new nuclear power station in Scotland by refusing planning consent.
However, during first minister's questions, he was challenged by Green MSP Shiona Baird over the coalition executive's commitment not to support the further development of nuclear power stations.
Labour and the Lib Dems have a partnership agreement which states that nuclear power remains off the agenda "while waste management issues remain unresolved".
Ms Baird asked the first minister to define the word "unresolved".
She asked if it meant waiting 25 years until a new storage site was built.
'We have the power'
Ms Baird also asked if the first minister would think the matter resolved when the government-appointed Committee for Radioactive Waste Management reports its findings in July 2006
Mr McConnell replied that it would be "decided upon, preferably by independent bodies".
He went onto to tell MSPs: "We do have the power to stop nuclear power stations being built in Scotland.
"We will use those powers until the issues of nuclear waste have been resolved, but that is a very clear position we have held, both parties hold it, we will stick together on this issue."
Later Ms Baird said: "Essentially Mr McConnell said the issue of nuclear waste will be resolved when it is resolved.
"He could not have fudged his answer more, leaving Scots completely in the dark about what the executive's position is on one of the most crucial questions facing Scotland."
The Greens also claimed that ministers were centralising planning powers and minimising opportunity for community input as a means of paving the way for developments such as new nuclear power stations that would otherwise be unfeasible due to widespread public opposition.
A recent report by Westminster's Scottish Affairs Committee demanded an audit of energy resources and suggested a renewed role for nuclear power and coal.
Two nuclear power plants generate much of Scotland's energy but they are reaching the end of their lives.
Hunterston B nuclear power station in Ayrshire is set to close in 2011 and Torness, in East Lothian, will last until 2023.
MPs have concluded that renewable energy and imports cannot plug the gap.