Just days before Usama Bin Laden (UBL) was finally killed in Pakistan, lawyers and the family of a Battersea man rubbished claims that he was one of his key operatives in Afghanistan.

Father of four Shaker Aamer has been held in Guantanamo for more than nine years without ever being charged with any offence, but classified documents posted on the Wikileaks alleged he was a “close associate” of UBL.

The allegations, which came in a Joint Task Force review of his case dated November 2007, also accused him of being a “recruiter, financier, and facilitator” for al-Qaeda.

Some allegations come from Mohammed Basardah, who was freed from Guantanamo after giving testimony that implicated 123 other prisoners, documents reveal.

Claims he made against Mr Aamer include him being “one of UBL's more significant operatives” who designed a system of changing radio frequencies during the fighting to avoid interception.

The Guardian newspaper pointed out Basardah made unsupported allegations against another British resident, Bisher al-Rawi - who was later released.

Mr Aamer’s father-in-law, Saaed Ahmed Siddique, said: “If any of this was true he would be in a court now.

The documents said he travelled to a lot of places, but that is not a crime. All of these claims have no basis.”

Clive Stafford Smith, a human rights lawyer and director of Reprieve - a charity working with some Guantanamo detainees - said the claims in the leaked documents would not stand up in court.

He said: “[Basardah] was promised all sorts of things. The conservative American judges have found him to be utterly incredible.”

He added: “How much [of these allegations] would stand up in court. “Essentially none of it, even in the incredibly loose world of Guantanamo litigation. But they [the US] only have to prove by preponderence and they can use secret evidence that he can’t see.

“These 759 documents are the worst a military person can concoct. Given that, I see lots of documents in cases, in one case 5,000 documents, the stuff in these documents is still drivel.”

The Save Shaker Aamer Campaign added: “We believe Shaker is being held because he is a victim and witness of torture.”

The UK’s foreign office minister Alistair Burt told the BBC Mr Aamer’s case would be raised with the US next month.

He said: “The best and the right thing we can do is to make sure we have contact at the highest level - that's why the foreign secretary has raised it with Secretary Clinton.

“That's why he will do so again, very shortly and will do so when Mrs Clinton is in the United Kingdom for a more extended period of time in May.”

He said: “It's why the deputy prime minister is taking it up. We believe we are doing the very best that we can by trying to meet any objections the United States might have and putting the case for Shaker Aamer to return to the United Kingdom."

Mr Aamer, a Saudi born, UK resident, was cleared for release in 2007.

He claims he was working for a charity in Afghanistan in 2001 when he was captured by the Northern Alliance and passed onto US forces.

Mr Aamer, who has never seen his youngest child, is believed to be one of the claimants that has settled with the UK Government over torture allegations.