On Wednesday the prime minister said the UK's commitment to the Gurkhas could be honoured "in a way that protects the public finances".

Campaign lawyer David Enright said victory seemed "a fait accompli, but we have had several false dawns before".

Some 36,000 Gurkhas who left before 1997 have been denied UK residency.

Details of the new rules have not yet been released, but it appears that these Gurkhas will now be allowed to live in Britain.

Home Secretary Jacqui Smith is expected to announce the new policy in a statement in the House of Commons at about 1215 BST.

Ms Lumley and other members of the Gurkha Justice Campaign want them to be given the same rights to settle as soldiers from Commonwealth countries who had fought for the UK.

The Nepalese Gurkhas serve in a brigade in the British army.

'Brilliantly-fought'

The prime minister suffered a shock Commons defeat on the issue, forcing ministers to reconsider existing rules on how many Gurkhas can settle in the UK.

It was followed by an extraordinary piece of Westminster theatre when Ms Lumley came face-to-face with minister Phil Woolas in BBC studios and quickly won public assurances over future policy at an impromptu joint press conference.

He added: "I believe it is possible for us to honour our commitments to the Gurkhas and to do so in a way that protects the public finances."

On Tuesday, officials from the Home Office and the Ministry of Defence met Gurkha groups at talks hosted by the home affairs committee.

Committee chairman Keith Vaz said he was "very pleased" with how the talks went.

Afterwards, the committee sent a letter to Mr Brown asking for all Gurkhas to be awarded full citizenship rights.

But Mr Enright said it was too early to celebrate victory.

"Although everyone here is celebrating, I'm not going to celebrate until I know for sure," he said.

Labour MP Martin Salter, who chairs a group of MPs calling for Gurkha rights, said the campaign inside and outside Parliament had been "long and brilliantly-fought".