The papers, filed in a $3,000 billion lawsuit in America, allege the deal was agreed after two secret meetings between Saudi royals and leaders of Al-Qaeda, including Bin Laden. The money enabled Al-Qaeda to fund training camps in Afghanistan later attended by the September 11 hijackers.

The disclosures will increase tensions between the United States and Saudi Arabia. An analyst at the influential Washington-based Rand Corporation think tank recently told a Pentagon briefing that Saudi Arabia was the “kernel of evil”.

The documents, based on investigations by lawyers for the September 11 victims and hitherto unpublished information from intelligence agencies, shed light on Al-Qaeda’s funding, naming the Saudi royals and detailing the network of charities and businesses through which Bin Laden raised money.

According to the lawsuit, the Saudi princes were deeply worried over attacks by Islamic fundamentalists on American servicemen at a US army training facility in Riyadh in November 1995 and at the Khobar Towers barracks in June 1996, in which 19 US airmen died.

They feared Bin Laden’s men, who had recently relocated to Afghanistan from Sudan, would attempt to destabilise the kingdom because of their opposition to the presence of US troops. They therefore decided to come to an accommodation with the terrorist leader.

The court documents say the first meeting was in 1996, when Saudi princes and business leaders met in Paris and agreed to give funds to Bin Laden’s organisation. Saudi Arabia’s secret service, the Istakhbarat, had already decided in late 1995 to fund the Taliban, then based primarily in religious schools in Pakistan.

A further meeting in Kandahar, Afghanistan, in July 1998 led to the deal between Saudi Arabia and the Taliban. Those present included Prince Turki al-Faisal al-Saud, then chief of the Istakhbarat, Taliban leaders, senior officers from Pakistan’s ISI secret service and Bin Laden.

Turki knew Bin Laden well, not just through family connections but because in the early 1980s he had hand-picked the young Saudi to organise Arab volunteers fighting the Russians in Afghanistan.

According to the documents, the agreement stated Bin Laden would not use his forces in Afghanistan to subvert the Saudi government. In return, the Saudis agreed to ensure that requests for the extradition of Al-Qaeda members and demands to close Afghan training camps by third countries were not carried out.

To reinforce the deal, the Saudis agreed to provide oil and financial assistance to both the Taliban and to Pakistan. The documents detail donations totalling “several hundred millions” of dollars.

The lawsuit also alleges that the Saudi royal family has supported charities with close ties to Bin Laden, including a $6m gift from the Saudi defence minister, Prince Sultan, to the International Islamic Relief Organisation, al-Haramain, the Muslim World League and the World Assembly of Muslim Youth.