The CIA repeatedly misled the US government over the severity and effectiveness of its interrogation methods, the Washington Post reports.
A long-awaited US Senate report said that the CIA used secret "black sites" to interrogate prisoners using techniques not previously acknowledged.
These included dunking suspects in icy water and smashing a prisoner's head against a wall.
The findings stem from the time of former President George W Bush.
Officials familiar with the secret document said that the CIA's interrogation program yielded little useful intelligence.
They also said that this intelligence had then been exaggerated so that the interrogation program looked more effective than it actually was.
The report is the result of a wide-ranging investigation by the Senate intelligence committee into CIA activities which began in 2009.
The committee will meet on Thursday to decide on whether to send a summarised version to President Barack Obama for eventual public release.
Internal divisions
Officials at the CIA's headquarters ordered officers to continue with harsh interrogations even after they were convinced that the prisoners had no more information to give, the Washington Post said.
One official said that almost all the valuable intelligence from al-Qaeda suspect Abu Zubaida was gained before he was waterboarded 83 times.
The report also spoke of divisions within the CIA in protest at the conditions prisoners were forced to endure.
A CIA spokesman told the Post the agency had not yet seen a final version of the report and so could not officially comment on its contents.
However, current and former officials told the paper privately that the 6,300 page study contained factual errors and misguided conclusions.
Earlier in March the head of the Senate intelligence committee accused the CIA of improperly accessing Senate computers during the investigation.
Senator Dianne Feinstein said that the alleged hacking "may have undermined the constitutional framework" of government oversight.
据《华盛顿邮报》报道，中情局（CIA）多次误导美国政府关于其调查方式的严重性和后果。
期盼已久的美国参议院的报告称，中情局将犯人关进秘密的“黑牢”，采取没有得到承认的审讯手段。
这些手段包括将嫌疑人浸入冰水里，或者将嫌疑人的头向墙上猛撞。这些发现都是发生在美国前总统布什任职期间。
知情官员说，中情局调查过程中获得的情报价值不大。他们还说，所获得情报价值被夸大，所以中情局的调查过程看起来富有成果，其实则不然。
该报告来自美国参议院情报委员会对2009年以来中情局活动广泛调查的结果。
委员会将在星期二举行会议，讨论是否要将该报道的总结版本发给贝拉克·奥巴马总统，以决定是否最终公开发行。
内部分歧
《华盛顿邮报》报道称，中情局总部官员命令下属继续采取残酷调查手段，即使他们已经确信不会在囚犯身上得到更多信息。
其中一位官员说，几乎所有来自“基地组织”嫌疑人阿布祖巴达的有价值情报都是在其遭受83次水刑后才得到的。报道还谈到了中情局内部关于抗议犯人被迫遭受酷刑上的分歧。
一位中情局的发言人告诉《华盛顿邮报》，中情局还没看到报道的最终版本，所以不能对其内容作出官方回应。但是，现任以及前任官员私下告诉该报称，这份长达6300页的报道存在错误的事实以及错误的结论。
三月初，参议院情报委员会负责人控诉中情局在调查中非法监控参议院官员的电脑。参议员戴安娜·范斯坦称，这些行为可能破坏了监督政府的宪政架构。
