A serving Scotland Yard officer was arrested today on suspicion of receiving illegal payments from journalists.
The 52-year-old woman, understood to be a member of the force's specialist operations branch, is being held in Essex after detectives swooped on her home at dawn.
She is the first police officer arrested under Operation Elveden, the inquiry into alleged illegal payments, which runs alongside the Operation Weeting phone-hacking investigation.
The specialist operations division in which she works covers some of the Met's most demanding roles, from counter-terrorism to protecting the Royal Family.
A Scotland Yard spokesman said she was arrested at 6am.
"Officers from Operation Elveden arrested a serving Metropolitan Police Service officer on suspicion of misconduct in a public office and offences contrary to the Prevention of Corruption Act 1906," a force statement said.
"The 52-year-old woman was arrested at a residential address in Essex and is currently in custody at an Essex police station."
Eight suspects have now been arrested as part of Operation Elveden, which was launched after officers were handed documents suggesting News International journalists had made payments to officers.
Elveden was launched in the summer after News International handed documents to Metropolitan Police officers.
Sir Paul Stephenson, the then Met commissioner, said in July that evidence from the publisher suggested a small number of officers were involved.
The final total of people whose phones were hacked by the News of the World will be about 800, the force believes.