Gurkhas are known for their bravery and fighting spirit
A government decision to limit the number of Gurkha veterans allowed to settle in the UK faces a parliamentary challenge from the Liberal Democrats.
They have secured a debate on the issue in the House of Commons on Wednesday.
Campaigners claim fewer than 100 of the Nepalese soldiers will benefit from the Home Office's offer of UK residency to Gurkhas who meet certain conditions.
The government insisted that changes to residency rules would allow an extra 4,300 former Gurkhas to settle.
Liberal Democrat leader Nick Clegg held talks with actress Joanna Lumley, who has spoken out on behalf of 36,000 Gurkhas denied residency because they served in the British Army before 1997.
Ms Lumley, whose father served in a Gurkha regiment, will join other campaigners for a demonstration outside Parliament when the debate is held.
Mr Clegg said the debate meant that a minister would have to "come and explain the government's insulting decision to turn their back on these brave soldiers".
"This is our best chance to force Gordon Brown to back down, even at this late stage," he said.
"People who are prepared to fight and die for this country should be entitled to live here.
"Yet even this basic principle is broken by a government desperate to cover its back and wriggle out of its commitments."
On Friday, immigration Minister Phil Woolas denied on the government had "betrayed" the Gurkhas, claiming the new rules would improve their situation.
"It has never been the case that all Gurkhas pre-1997 were to be allowed to stay in the country. With their dependants you could be looking at 100,000 people," he added.
Campaigners have vowed to continue their fight against the conditions laid down by the government.
These require Gurkhas wishing to settle in the UK to meet criteria relating to long service, bravery medals and medical conditions caused by service in the brigade.