The UK's counter-terrorism chief has condemned as "beneath contempt" people who leak anti-terrorism intelligence.
Peter Clarke: Leak warning
Deputy Assistant Commissioner Peter Clarke of the Metropolitan Police said there were a "small number of misguided individuals who betray confidences".
By doing so, they had compromised investigations, revealed sources of life-saving intelligence and "put lives at risk" during major investigations.
DAC Clarke also warned of a damaging "lack of public trust" in intelligence.
In a major speech at the Policy Exchange, a think-tank, DAC Clarke said his role as National Co-ordinator of Terrorist Investigations was to bridge the intelligence and policing worlds in an environment that had completely changed in recent years.
Some 100 suspects were awaiting terrorism trials, he said.
But he warned the police's efforts to counter terrorism threats had been damaged by leaks to the media.
"The recent investigation in Birmingham into an allegation that a British serviceman had been targeted by a terrorist network is but one example of this," said DAC Clarke.
"On the morning of the arrests, almost before the detainees had arrived at the police stations to which they were being taken for questioning, it was clear that key details of the investigation and the evidence had been leaked.
"This damaged the interview strategy of the investigators, and undoubtedly raised community tensions.
"I have no idea where the leaks came from, but whoever was responsible should be thoroughly ashamed of themselves."
The counter-terrorism chief said the situation had been made worse by allegations that police were politically "partial" after the parliamentary row over extending the time that terror suspects could be held without charge.
But he also said he was frustrated that while it took a long time to bring complicated terrorism cases to court, the public were losing out in their ability to understand what the security services were trying to tackle.
British law placed restrictions on what officials could say in public and what the media reported. Foreign media, however, were publishing and broadcasting details of the same terrorism cases - details available to the British public via the internet.
"I just wonder if we could be bolder and, dare I say it, trust juries to distinguish the prejudicial from the probative," he said.
"Apart from anything else, I honestly believe that the public are entitled to know why airport security is becoming ever more intrusive and inconvenient," he said.