A conference call between Scotland Yard and the FBI was intercepted and published by hackers, the group Anonymous has claimed.
Police and the FBI discussed details of investigations into ongoing cases against Anonymous and other groups, dates of planned arrests, and potential evidence during the recording of the 17-minute conversation, which was posted on YouTube.
Anonymous also published an email, purporting to be from the FBI, giving details of the access code for the call and the email addresses of those invited to take part.
Writing on its Twitter account, AnonymousIRC said: "The FBI might be curious how we're able to continuously read their internal comms for some time now."
The FBI said the information "was intended for law enforcement officers only and was illegally obtained".
According to the leaked email, which appears to have been written by the FBI's Timothy Lauster Jr, the call took place on January 17. During the call, the officers and agents discussed the names of people they were tracking, plans for legal action and requests for more time.
The Scotland Yard officers also joked about a conference on cyber-crime in Sheffield, telling the FBI that they had not missed much by not having visited the city before, adding it was "not exactly a jewel in England's crown".
One of the FBI agents also thanked UK police for their support and for trying to give the FBI more time, saying: "I just want to express our gratitude for being flexible on this. I know New York (FBI office) appreciates it, and the FBI as a whole."
One of the UK officers replied: "We're here to help. We've cocked things up in the past, we know that... It's not that much of a hardship."
Anonymous is a loosely-organised group of hackers which has claimed responsibility for attacks against corporate and government websites all over the world. The group also claimed to have disrupted the websites of Visa and MasterCard in December 2010 when the credit card companies stopped processing donations to WikiLeaks and its founder, Julian Assange.