A former senior aide to David Cameron is facing trial at Southwark crown court accused of making and possessing scores of child abuse images.

Patrick Rock, 63, who was one of the government's chief advisers on policy for online pornography filters, appeared at Westminster magistrates court in London on Thursday. He was charged with three offences of making child abuse images and one of possessing 62 indecent images of children. Crown Prosecution Service lawyers assessed the images as level C, the lowest category.

Standing alone in the glass-fronted dock, Rock spoke only to give his name, date of birth and address during the short hearing before the district judge, John Zani.

Prosecutor Ruona Iguyovwe told the judge that Rock's government position "aggravates the circumstances of this case" and that it should be transferred to the crown court.

Igvyovwe said the charges related to alleged offending in the US, where Rock had been living and working until recently.

Zani bailed Rock to return to Southwark crown court on 17 July. Under his bail conditions, Rock must surrender his passport to police, reside at his home in Fulham, west London, and maintain contact with a welfare officer.

The court heard that Rock is in regular contact with a welfare officer provided by an unnamed previous employer. Downing Street and the Conservative party denied they were providing the officer.

Rock was arrested at his home in February. He resigned from his post as deputy head of Cameron's policy unit following his arrest, which was not made public until the details were published by the Daily Mail three weeks later.

The National Crime Agency said last week that Rock had been charged with possessing 59 indecent images of children, but that figure rose on Thursday when Iguyovwe said the former Whitehall official was now accused of keeping 62 category C images on an iPad.

The offence of making indecent images of children carries a maximum sentence of 10 years' imprisonment under section 1 of the Protection of Children Act 1978. Possessing child abuse images has a statutory maximum of five years' imprisonment under section 160 of the Criminal Justice Act 1988.

In a statement last week Judith Reed, a senior lawyer with the CPS organised crime division, said: "The decision to prosecute has been taken in accordance with the code for crown prosecutors.

"We have determined that there is sufficient evidence for a realistic prospect of conviction and that a prosecution is in the public interest."

Rock's barrister Christine Agnew told the court her client was of "impeccable character" and had voluntarily handed himself in to police.

• This article was amended on 3 July 2014 to clarify who was providing a welfare officer for Rock.