An internal briefing by defence giant Babcock, distributed by the Better Together campaign, said "it is unlikely that Clyde as a conventional naval base would require the same numbers of support personnel particularly when the number of naval personnel will reduce significantly".
But the Scottish Government said it anticipates Faslane will require the same number of military personnel that it has at present, as well as a large number of civilian jobs, as it makes the transition to become Scotland's main naval base and joint force headquarters.
Speaking on behalf of Better Together, Labour MSP Jackie Baillie, whose Dumbarton constituency includes Faslane and Coulport, said: "It is clear that if Scotland leaves the UK then the jobs of 11,000 workers on the Clyde would be at risk. The nationalists' plans don't come anywhere close to providing that level of employment in the future.
"This would not only devastate the families of the workers involved but also the local economy in my constituency too."
A spokesman for Deputy First Minister Nicola Sturgeon said: "Transitional arrangements will support both the day to day operations and the workforce levels at the base.
"We anticipate the same number of military personnel as now as well as a large number of civilian jobs - both during the transition phase and thereafter.
"Of course defence contractors such as Babcock and other companies in the sector will be very well placed to secure defence contracts both during and after the transition.
"Work to reconfigure Faslane is expected to involve major construction activity, and thus will also help create and protect jobs in the area.
"The Scottish Government expects that, at the end of the transition, the number of military personnel at Faslane will approximately match numbers there currently, and be supported by a significant number of civilian personnel. Given this continuing commitment to jobs on the Clyde it's no wonder that veterans of the UCS (Upper Clyde Shipbuilders) work-in are backing a Yes vote in September"
Derek Torrie, Unite convenor at Faslane and Coulport, said: "Those of us working at Faslane and Coulport are in no doubt that the security of our jobs is best served by remaining in the United Kingdom. Any other outcome is a threat to our future employment."