Alex Salmond's plans to defend an independent Scotland appear underfunded and are lacking in crucial detail, a parliamentary report says.
MPs also took a swipe at the Ministry of Defence for its apparent failure to begin planning for a division of military assets if Scots vote next September to leave the United Kingdom.
The Commons defence select committee was highly critical over the paucity of information produced by the Scottish National Party during the independence debate about its defence and security plans.
It said it unconvinced that the proposed £2.5bn budget was enough for a new Scottish defence force and to pay for new equipment such as submarines and fast jets.
The MPs warned that Scottish defence companies would face a difficult future in a breakaway nation as new contracts from Edinburgh would be dwarfed by the loss of orders from the UK Government.
Their report called for more detail on the navy and raises a number of questions about the size and scope of a Scottish army, including costs, troop numbers and base locations.
On plans for an air force, the report said: “We do not currently understand how the Scottish Government expects, within the available budget, to mount a credible air defence - let alone provide the additional transport, rotary wing and other support aircraft an air force would need.”
Moving the Trident nuclear deterrent - which the Scottish Government has pledged to scrap - from the Clyde to a new site in the remaining UK would take years to achieve, it said.
The committee chairman, James Arbuthnot , said becoming nuclear-free could hamper Scotland's hopes of joining Nato. He said “Nato is a nuclear alliance and any action likely to disrupt the operation of the UK's strategic deterrent would undoubtedly influence Nato member countries' attitudes towards an application from Scotland.”