Some 500 individuals have so far expressed interest in joining the claim, and about £10,000 compensation could be due each one.
MoD housing policy requires personnel under the age of 37, or over the age of 37 and unmarried, to pay for single living accommodation while those over 37 and married are eligible for an accommodation allowance.
Leigh, Day solicitor Ryan Bradshaw said: ‘The MoD has made some progress tackling the unfairness in its housing policies, but it is highly unlikely to compensate people for their losses unless they bring a legal claim against it.’