A government decision to limit the number of Gurkha veterans allowed to settle in Britain faces a parliamentary challenge from the Liberal Democrats.
The BBC reports they have secured a debate on the issue in the House of Commons on Wednesday.
The Home Office said on Friday that new immigration rules would give around 4000 former members of the Nepalese unit that has fought for Britain since 1815 the right to settle, along with 6000 dependents.
But campaigners say restrictions imposed by the government mean fewer than 100 Gurkhas would qualify.
The rules apply to Gurkhas who left the army before 1997 and who do not share the same rights to settlement enjoyed by colleagues discharged after that date.
The government issued the revised immigration guidelines after a High Court judge ruled last October that existing policy was unlawful.
The government fears as many as 100,000 former Gurkhas and their families might seek to come to Britain if the restrictions were not in place.
Campaigners put the number no higher than 8000 and said the new guidelines were more restrictive than the ones they replaced.
The new rules allow Gurkhas who retired before 1997 to settle in Britain if they meet one of five criteria: including 20 or more years' service, a gallantry medal or a long-term medical condition attributable to their service.