Shaker Aamer, the last British resident held at Guantanamo Bay, is to be released, a British Government spokesman said.

The US government has notified the UK authorities that it now intends to return Mr Aamer to Britain.

"The Government has regularly raised Mr Aamer's case with the US authorities and we support President (Barack) Obama's commitment to closing the detention facility at Guantanamo Bay," the spokesman said.

"In terms of next steps, we understand that the US Government has notified Congress of this decision and once that notice period has been concluded, Mr Aamer will be returned to the UK."

Mr Aamer, 46, a Saudi national, was originally detained in Afghanistan in 2001.

He was subsequently transferred to Guantanamo Bay where he has been held without charge.

His release is expected to take place once the 30 day notice period set by the US authorities has expired Mr Aamer has been the subject of a long campaign to secure his release. Amnesty International UK Director Kate Allen said the news of his return was a "huge relief".

"In the past Mr Aamer has reportedly been at death's door during a hunger strike and his return to his family in Britain won't come a moment too soon," she said.

"The immediate focus should now be on providing medical and other support for Mr Aamer on his return to the UK, but let's not forget that his 13-year ordeal at Guantanamo has been an absolute travesty of justice."

Conservative MP David Davis, who has repeatedly called for Mr Aamer's release, said it was "great news".

He told the Press Association: "It is long overdue. It should have happened years ago - 13 years without having been charged with or indeed accused of any crime.

"It is brilliant news for his family, who are British citizens, very good news for him and good news for justice.

"I would like to give my commendation to the large number of people who have campaigned year in and year out for Shaker Aamer's release. For them this is a very great vindication."

Mr Davis said the process of releasing those held in the facility has been "pretty painful for the American government".

He said: "Let's hope (Mr Aamer's release) is implemented as quickly as humanly possible."

Successive British governments have pursued a policy of pressing for the release of UK nationals and residents held by the US at the Guantanamo Bay detention facility on Cuba.

David Cameron raised Mr Aamer's case with Mr Obama when they met in January and the decision to return him to the UK him was discussed by the two leaders again in a phone call on Thursday.

Officials would not discuss under what conditions he was being released.

However, it is thought Mr Aamer - who described as a "close associate of Osama Bin Laden" who fought in the battle of Tora Bora in US files obtained by the WikiLeaks website - will be subject to monitoring by the security services on his return.

The Government spokesman said: "As the US has said, we have one of the most robust and effective systems in the world to deal with suspected terrorists and those suspected of engaging in terrorist related activity and we will continue to do all we can to protect people in Britain and around the world from the threat of terrorism."

A senior US defence official said the final decision to return Mr Aamer to the UK had been approved by US Defence Secretary Ashton Carter.

The move was said to have followed a "thorough review of his case and taking into consideration the robust security assurances that will be provided by the British government, one of our strongest allies who has supported our efforts to close the detention facilities at Guantanamo Bay".