Watch live coverage
as the Scottish Affairs Committee continues its inquiry into the referendum on Scottish independence, from 2.20pm on 25 April 2012.
The Scottish government plans to hold a referendum on independence in the autumn of 2014.
Opponents of the move say the delay is creating great uncertainty for Scotland and its economy.
Because constitutional matters are not presently devolved, Scottish Secretary Michael Moore has said that any referendum held without Westminster's backing would not be legally binding and, therefore, open to legal challenge.
UK ministers are in talks with the Scottish government on devolving powers, which they say are needed to make the referendum legally watertight.
The SNP wants to lower the voting age in the referendum to let 16 and 17-year-olds participate, in keeping with long-standing policy, but opposition parties oppose the move.
The committee will hear from Armed Forces Minister Nick Harvey and Defence Minister Peter Luff; and representatives from the Confederation of Ship Building and Engineering Unions.