There have been 266 fires on nuclear submarines in the past 25 years, it has emerged.
The incidents included 74 blazes on ballistic missile submarines.
Three happened while the vessels were in base, one of those on a ballistic missile boat.
Peter Luff, minister for defence equipment, support and technology, gave the figures in response to a parliamentary question by SNP defence spokesman Angus Robertson.
Mr Robertson said the “apparent vulnerability” to fire events on these vessels raises “grave questions” for UK ministers.
He said: “Any one of these fires could have had catastrophic consequences and the frequency of these incidents raises the most serious safety concerns.
“That so many of these incidents occurred on submarines that may have been nuclear armed is deeply troubling.”
A ministry spokesman said: “No fire on board any Royal Navy submarine has ever had an impact on nuclear safety”