Senior police officer April Casburn "undermined" phone hacking investigations when she called the News of the World offering information, a court heard.

April Casburn (Reuters)

Detective Chief Inspector April Casburn, 53, is accused of leaking details of Operation Varec to the defunct tabloid in 2010.

In a phone call made to the paper on the September 11 2010, prosecutors say she revealed suspects and outlined legal issues facing the phone hacking inquiry.

Prosecutor Mark Bryant-Heron said the call was "malicious" and intended to destabilise the investigation. Taking the stand on day three of the trial, prosecutor Mark Bryant-Heron said there was "nothing that threatened counter terrorism" and that Ms Casburn may have felt "annoyed" and "isolated" at the prospect of officers from her department being assigned onto phone hacking investigations.

Ms Casburn, who managed the National Terrorist Financial Investigation Unit, denies misconduct claiming she was "angry" at what she saw as the diversion of life saving resources.

She said she did not ask for cash but had been forced to contact the press as it was the "only way" she had to influence senior colleagues to move the investigation out of counter-terrorism command.

"It's like having a criminal investigation and going to the suspect and telling them what you are up to" - Prosecutor Mark Bryant-Heron

But Mr Bryant-Heron said: "It may have been it pushed her over the edge, though she denies it, that the use of that financial investigator bypassed her position and she was feeling out of the loop, but she made what I suggest to you was a malicious call."

He urged the jury to consider why Ms Casburn opted to call the now-defunct tabloid at the centre of the phone hacking allegations, when it was the Guardian and Independent that had led much of the phone hacking coverage. "It's like having a criminal investigation and going to the suspect and telling them what you are up to," he said.

He added: "Without wanting to sound like Humphrey Bogart, of all the papers in all the world who did she go to?"

Summing up the evidence, Mr Justice Fulford said the prosecution must prove two things: that what Ms Casburn did was wrong and fell substantially below the standards the public are entitled to expect of police officers; and that she acted deliberately.

Ms Casburn, of Hatfield Peverel, Essex, denies misconduct in a public office. The jury begins its deliberations tomorrow morning.