The Taliban in Afghanistan are being directly assisted by Pakistani security services, according to a secret Nato report seen by the BBC.

The leaked report, derived from thousands of interrogations, claims the Taliban remain defiant and have wide support among the Afghan people.

Meanwhile, Pakistan's Foreign Minister Hina Rabbani Khar says her country has no hidden agenda in Afghanistan, in response to the leaked secret report.

Speaking at a news conference in Kabul with her Afghan counterpart yesterday, Khar said allegations in the report were "old wine in new bottles".

The report—on the state of the Taliban — fully exposes for the first time the relationship between the ISI (Pakistan's intelligence service) and the Taliban, BBC's Quentin Sommerville says.

It is based on material from 27,000 interrogations with more than 4,000 captured Taliban, al-Qaeda and other foreign fighters and civilians. It notes: "Pakistan's manipulation of the Taliban senior leadership continues unabatedly". The report says that Pakistan is aware of the locations of senior Taliban leaders.

Refuting the report, Pakistan's foreign minister said "We can disregard this as a potentially strategic leak."

The two countries should stop blaming each other for cross-border problems, she added.

"Senior Taliban representatives, such as Nasiruddin Haqqani, maintain residences in the immediate vicinity of ISI headquarters in Islamabad," the report said.

"We have long been concerned about ties between elements of the ISI and some extremist networks," said US Pentagon spokesman Captain John Kirby, adding that the US Defence Department had not yet seen the report.

Adm Mike Mullen, former chairman of the US Joint Chiefs of Staff, has explained Pakistan's closeness to the Afghan Taliban by pointing to infiltration of its army by the religious right, but he also says it is part of a grand strategy to increase leverage in the region via "proxies".

Despite Nato's strategy to secure the country with Afghan forces, the secret document details widespread collaboration between the insurgents and Afghan police and military.

Lt Col Jimmie Cummings, a spokesman for Nato's International Security Assistance Force (Isaf) in Afghanistan, said the document was "a classified internal document that is not meant to be released to the public".

"It is a matter of policy that documents that are classified are not discussed under any circumstances," he said.

The report also depicts the depth of continuing support among the Afghan population for the Taliban, our correspondent says.

It paints a picture of al-Qaeda’s influence diminishing but the Taliban's influence increasing, he adds.

In a damning conclusion, the document says that in the last year there has been unprecedented interest, even from members of the Afghan government, in j oining the Taliban cause.