Downing Street adviser Patrick Rock charged with making and possessing indecent images of children.
Patrick Rock, who was involved in Government policy on filtering online child abuse images, resigned shortly before his arrest in February.
The 63-year-old has had a glittering career as a Conservative Party adviser spanning 30 years and in the 1970s was credited with coining the slogan "cows moo, dogs bark, Labour puts up taxes".
On Friday, he was charged with three offences of making indecent images of children and one offence of possession of 59 indecent images of children.
The four charges cover alleged offences committed between 31 July and 31 August 2013.
The pictures have been classed as level C by the Child Exploitation and Online Protection Centre (CEOP), defined as "indecent images depicting erotic posing with no sexual activity".
Mr Rock, a special adviser on policy, was arrested at his home in the early hours of 13 February and had resigned the day before.
The matter did not come to light until almost a month later, when a national newspaper's enquiries forced Downing Street to release a statement confirming the rumours.
Asked about the charges at a press conference after an EU summit in Brussels on Friday, the Prime Minister said: "I won't be saying anything.
"It would be purely a matter for the courts and it wouldn't be appropriate to comment."
Mr Rock has been an influential figure behind the scenes in the Conservative Party for decades and unsuccessfully stood as an MP three times.
He met David Cameron when they were fellow advisers to the then Home Secretary, Michael Howard, in the 1990s and the Prime Minister brought him into the Downing Street policy unit in 2011.
Judith Reed, a senior lawyer with the Crown Prosecution Service's organised crime division, said: "We have determined that there is sufficient evidence for a realistic prospect of conviction and that a prosecution is in the public interest."
Mr Rock has been bailed to appear at Westminster Magistrates' Court on 3 July.
Additional reporting by PA
Comment: So, was Rock actually a pedophile? A pedophile hung out to dry when he posed some sort of threat to the system? Or framed because of what he might have known from working on government policy on child abuse? Se also: