Dr Myles Bradbury pleads guilty to string of offences against children in his care at Addenbrooke's hospital in Cambridge

A children's doctor at Addenbrooke's hospital in Cambridge has admitted sexual offences against young cancer patients in his care.

Dr Myles Bradbury, a 41-year-old paediatric haematologist, appeared at Cambridge crown court. He pleaded guilty to six counts of sexual assault, 13 counts of engaging in sexual activity with a child and three counts of causing or inciting a child to engage in sexual activity.

Bradbury, wearing a dark suit and blue tie, also admitted one count of voyeurism and two counts of making indecent images of a child. The offences involved 18 complainants, said John Farmer, prosecuting.

Bradbury was bailed and told he must sign the sex offenders register. He pleaded not guilty to a count of sexual activity with a child and a count of sexual assault. Judge Gareth Hawkesworth said these two counts would probably remain on file.

No date was set for sentencing but the judge said Bradbury could expect a substantial custodial term. As he left court, Bradbury told reporters: "I'm so sorry." He refused to answer further questions.

Police said more than 16,000 indecent images of children were found on a disk at his home. A spokesman said there were likely to be more victims.

Dr Keith McNeil, the chief executive of Cambridge University hospitals trust, which runs Addenbrooke's, said: "It is hard to put into words just how saddened we are that this situation has occurred, and our most abject and sincere apologies go out to any and all of our patients and their families who are affected by this in any way.

"As chief executive of the trust, I am so deeply sorry these incidents have happened and I am also deeply saddened, as a doctor, that one of my own profession has placed himself and his patients in this position. There is a very ancient and sacred trust that exists between a doctor and his patients and, quite frankly, it sickens me to think that trust has been breached."

Ann-Marie Ingle, the trust's chief nurse, said she and the rest of the staff had been shocked by Bradbury's "cold and calculating abuse of trust".

Police said Bradbury was interviewed three times but refused to say anything. His offences involved 18 victims aged from eight to 17, and were carried out between 2009 and last year. His abuse came to light after a victim spoke to his parents about what had happened and Bradbury was suspended by the NHS last November before being arrested the following month.

Ingle said: "I cannot begin to express how sorry I and all of my colleagues are for the distress that Myles Bradbury's abuse caused to patients and their families. Our thoughts, and ongoing support, are with the families and children who are affected by these charges.

"His cold and calculating abuse of trust has deeply shocked us all, including staff who worked alongside him to care for these vulnerable and sick children. As soon as we were alerted, we took immediate action to suspend him from clinical practice and we have worked closely with the police and the NSPCC over these past months.

"The actions of one individual should not taint the public's trust in the NHS and the care it provides. I would like to reassure patients and families that our staff working in children's services here at Cambridge University hospital continue to provide the care which our patients expect and can rely on."

DS Shane Fasey said: "Bradbury's offences were an appalling breach of trust committed against vulnerable victims who had been placed in his care. The families believed the boys were in his safe hands but they were actually being abused by Bradbury, who carried out examinations purely for his own sexual gratification and with no medical justification whatsoever."

Anyone who may be affected can call a helpline on 0800 389 8625.