Why won't the government tell us how many Scottish jobs rely on Trident?

The previous Labour government published figures stating how many Scottish jobs at the Faslane submarine base relied directly on the Trident nuclear weapons system.  (In case you're wondering, the figure was a surprisingly small 464 jobs).

The Coalition government has now been asked the same question, but has refused to give an answer.  Is this the result of nervousness about the looming Scottish independence referendum, the controversial plan to replace Trident, or embarrassment at how few jobs military spending creates?