The agency was responding to a Sunday Mirror report that the widow of Corporal Kumar Pun was told she had no right to stay in the UK the day after his death.
Kumar was among four soldiers killed in southern Afghanistan´s Helmand province on Thursday.
Kumar, from the 1st Battalion The Royal Gurkha Rifles, was killed along with Sgt Ben Ross, from 3rd Regiment, Royal Military Police, in a suicide attack while on patrol in Gereshk.
The Sunday Mirror claims that the following day officials told his widow -- who lives in Dover, Kent -- that she and their two daughters could be ordered back to Nepal when her visa runs out next year.
They could then be made to reapply for a British visa to return to the UK, a relative was quoted as saying.
But a UK Border Agency statement said: "We will not curtail this lady´s leave. We would not seek to remove the widow of any soldier killed in action, whether they are a Gurkha, a foreign or a Commonwealth soldier.
"A soldier´s spouse or dependents would almost certainly be granted settlement after applying for leave to stay in the UK."
Kumar, the son of a British Gurkha, was on his first deployment to Afghanistan after operations in Kosovo and Bosnia.
The 31-year-old was part of a team delivering training and mentoring to the Afghan National Police.
His commanding officer, Maj Chris Conroy, described Cpl Kumar as "unstintingly professional, calm and respectful of all, never failing to help and always willing to volunteer".
"On operations in Afghanistan he was steadfast, brave and a true leader," Major Conroy said.
"He looked after his soldiers as if they were his own, caring for them and watching over their every move."
Actress Joanna Lumley, a high-profile campaigner for Gurkhas´ residency rights, told the Mirror: "It just goes to show the Gurkhas are at the centre of the Army and are willing to fight for the British and give up their lives for this country."
The other soldiers killed in Afghanistan on Thursday included Rifleman Adrian Sheldon, 25, from 2nd Battalion The Rifles, who died in a separate explosion. Cpl Sean Binnie, 22, of the Black Watch, was shot dead.
Earlier, the Sunday Mirror claimed that Kumar´s wife, Parbati, was told that she has no right to stay in Britain – just 24 hours after he was blasted to death by a Taliban suicide bomber.
Speaking at Kumar and Parbati´s home in Kent, Kumar´s uncle Jak Phagami said: "She was told by an Army person that when her visa runs out she may have to go back to Nepal and reapply for a British visa so she can come back.
"She is totally distraught. She hasn´t eaten for two days or left her bedroom. She is slipping in and out of consciousness and we are really worried for her health."
Kumar, who had been in Afghanistan for just a month, was on patrol in the market town of Gereshk when a suicide motorbike bomber struck. As the soldier got out of his his Vixen Snatch vehicle, the jihadist raced towards him, blowing himself up as soon as he got close enough.
Kumar, a corporal praised by Army top brass for his bravery and professionalism, joined the Army in 1996 when he was 17.
His father Dhanbahadur Pun, 60, had also served in the Gurkhas and he was born in Hong Kong when Dhanbahadur was stationed there.
In 1999 he wed childhood sweetheart Parbati, but she was not allowed to come to Britain to live with him until 2006, when their daughter Klaudine was three.
They set up home together in Dover, where Parbati, now six, and their second daughter Petrina, 18 months, are settled.
But Parbati´s temporary visa is valid only until September 2010 – at which point she faces having to return to Nepal to apply for British residency, with no guarantee it will be granted by immigration officials.
Klaudine was born in Nepal and Petrina in Brunei, where Kumar was stationed. Neither is a British citizen and their visas also run out next September.
Meanwhile, it emerged that Parbati may not even be entitled to a war widow´s pension under MoD rules about length of service. A Justice for Gurkhas Campaign military lawyer said Gurkhas needed to serve 15 years alongside British forces to gain their pension. Kumar had served just under 14 when he was killed.
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