The CIA carried out “brutal” interrogations of al-Qaeda suspects in the years after the 9/11 attacks on the US, a US Senate report has said.

The summary of the report, compiled by Democrats on the Senate Intelligence Committee, said that the CIA misled Americans about what it was doing.

The information the CIA collected this way failed to secure information that foiled any threats, the report said.

In a statement, the CIA insisted that the interrogations did help save lives.

“The intelligence gained from the programme was critical to our understanding of al-Qaeda and continues to inform our counterterrorism efforts to this day,” Director John Brennan said in a statement.

However, the CIA said it acknowledged that there were mistakes in the programme, especially early on when it was unprepared for the scale of the operation to detain and interrogate prisoners.

The programme – known internally as the Rendition, Detention and Interrogation programme – took place from 2002-07, during the presidency of George W Bush.

Suspects were interrogated using methods such as waterboarding, slapping, humiliation, exposure to cold and sleep deprivation.