A leaked email obtained by the Sunday Herald shows that in April the Cabinet Office asked the Ministry of Defence (MoD) in April to "cascade" pro-Union material down through the ranks using direct email and internal websites. Civilian defence personnel were also issued with the material.
The Queen's Regulations, the long-standing rules governing the armed forces, say political activity is not allowed on service premises.
Section J5.582 states: "All forms of political activity, including political meetings and speeches, are prohibited in Service establishments.
"Information about party programmes or policies is not to be made available through Service journals or information rooms; nor is any propaganda issued by or on behalf of a political party to be distributed in Service institutions.
"No publicity is to be given in Service establishments to meetings, fetes, or similar activities having a political association."
One military recipient described the MoD material as "propaganda" and said it was "disappointing" to receive it through regimental lines.
The literature included the Westminster government's booklet Our Place In The World, which focuses on the UK's international standing and warns Scotland would be diminished if it left the UK.
Described as a "comprehensive overview [which] gives you the facts you need to make an informed choice", the booklet states "Scotland has a strong place in the world as part of the UK" and "we already have the best of both worlds" in the UK.
At the same time it was circulated, military brass were also telling service personnel "and their spouses/partners of their eligibility and entitlement to register as a service voter".
The SNP last night accused the UK Government of the "totally inappropriate" politicisation of the armed services.
Westminster confirmed that the leaflet had been sent out to all UK government employees, including civilian and military personnel in the MoD, but insisted that the matter was not a political one. A source said: "It is Government policy to maintain the UK and as such it is not a 'political issue' and we are not politicising civil servants or the military.
"It's important that employees are informed about government policy. We are not promoting one policy over another, as we have only one - to maintain the union."
Emails obtained by the Sunday Herald show that on April 29, the UK government issued a notice to senior army officers asking them to circulate the leaflet as widely as possible.
It said: "Please see attached the UK Government's Our Place In The World pack, the latest in a series of 'In The Know' information packs on Scotland ahead of the forthcoming referendum.
"The Cabinet Office has requested that MoD cascade the information pack via internal channels to all staff.
"Therefore, please can all business units share the pack through suitable means with military and civilian personnel, for example by hosting on intranet pages and email directly to staff."
A second leaked email, sent on May 12 by Major Mark Hobbs, deputy chief of staff at 51 Infantry Brigade and Army headquarters in Scotland, discussed voter registration.
It said every unit should tell its personnel about voter registration for both the referendum and the 2015 general election.
The email provided links to defence instruction notices on voter information, including one "specific to the Scottish Referendum", and added that the deadline for registration was September 2. Referring to the Our Place In The World booklet, Hobbs ended with "Att [attached] to this email is information released by the Cabinet Office on Scotland ahead of the forthcoming referendum".
The emails were sent a few weeks after the First Sea Lord Admiral George Zambellas warned that Scottish independence would damage "the very heart" of Britain's maritime defences and weaken the Royal Navy.
Angus Robertson, SNP leader at Westminster and the party's defence spokesman, said: "It is totally inappropriate for the armed forces to be politicised in this way.
"Disseminating 'propaganda' from one side of the referendum in the same emails as promoting voter registration is a misuse of office.
"That service personnel themselves described this as 'propaganda' speaks for itself.
"The UK Government and MoD have crossed a long-respected line to ensure the armed forces are not misused politically."
A Cabinet Office spokesperson said: "The Scotland Analysis papers and information packs are publicly available documents looking at Scotland's place in the UK and how Scotland benefits from and contributes to the UK.
"Since the UK Government's policy is to maintain the United Kingdom, it is legitimate and necessary for civil servants to support ministers as fully as possible in pursuit of this objective, in a way which maintains political impartiality and is in line with the requirements of the Civil Service Code."