Whitehall "spies" may already be embedded in the civil service in Scotland ready to leak intelligence in the event of independence, a former British civil servant has suggested.
James Aitken, formerly involved in overseas development, said "sleepers" may have been placed "ready to be activated as required".
Scotland would be at a "considerable disadvantage" in the negotiations that would follow a Yes vote, Mr Aitken wrote in The Scottish Review.
Scottish negotiators with little international experience other than fish talks and a few trade missions would face a "formidable" team ready to secure the best deal for the remainder of the UK, he said. The UK may also get help from US intelligence agents keen to safeguard the UK nuclear deterrent, he said, while the best Scottish negotiators could hope for is a few "spilled beans" from Whitehall.
Mr Aitken managed British aid programmes to a number of developing countries including Kenya, Uganda and India during his time at Whitehall.
He said: "It's a fair bet that any paper produced on independence by St Andrew's House will be circulating in Whitehall's red boxes within 24 hours, along with reports on discussions in private office and ministerial exchanges.
"Sigint (signal intelligence) can provide access to the computer system while Humint (human intelligence) will fill in the gaps. It would be surprising if 'sleepers' have not been embedded in St Andrew's House and Victoria Quay, ready to be activated as required."
He added: "The US has made it plain in the past that a nuclear-armed UK is in US interests. It follows that any threat to the UK deterrent is a threat to the US and our security services can look to support from US agencies even in activities which might be considered dubious under UK law."
Scottish Secretary Michael Moore has said Scotland would enter post-independence negotiations from "a position of weakness", in contrast to the diminished but still "comparatively large, wealthy and powerful" UK.
Deputy First Minister Nicola Sturgeon has predicted everyone will rally round in the event of independence to secure the best deal for "Team Scotland", regardless of their current political position.