A young man who dreamed of becoming a police officer has been jailed for child sex offences - including a sickening attempt to "blackmail" a 12-year-old schoolgirl into sending him indecent images of herself.

Cameron Longstaff, 20, went online to target the two schoolgirls, telling one he would circulate an intimate image of her that he had acquired if she did not send him more explicit pictures.

The youngsters said the experience left her feeling vulnerable, scared, and angry.

The other girl was so afraid she stayed indoors with the curtains closed, and asked her parents to always lock the doors.

As he imposed a year-long jail term on the defendant, of Hurley Road, Little Corby, Judge James Adkin told him that despite positive character references, the "overwhelming" evidence of his guilt from the trial revealed a darker side Longstaff's character, including his interest in child pornography.

"There is a predatory aspect to this," said the judge. "You felt it necessary to humiliate a young girl because she would not comply with your demands."

Longstaff denied two counts of inciting a child to engage in sexual activity; three of downloading indecent child images; one of possessing such images; and two counts of distributing it.

A jury convicted him of all the offences.

The court heard how Longstaff had amassed a large collection of sickening child pornography images, both still images and videos.

Of these, 33 were classed as the most serious kind. The trial was told how Longstaff - 16 when he committed most of the offences - used a social media site under a false name, targeting the two 12-year-olds, urging them to share indecent images of themselves.

When one refused he threatened to distribute an intimate image of her that he had acquired, later sending it to a Russian website used by child porn perverts.

Victim impact statements revealed how the girls were affected. The first girl was left suffering from sleep problems, and her school-work suffered.

The second girl - in court with her mother for the hearing - said: "I was hiding in the house with all the curtains drawn because the [the defendant] said he would come to my house."

Her mother said: "My daughter was only 12 years old and she was very scared by what happened. ..We had been an open house until then, but after the incident, my daughter insisted on locking all the doors all the time.

"She still feels uncomfortable now being at home alone."

Kim Whittlestone, for Longstaff, said her mitigation was limited because the defendant continued to protest his innocence. Character references showed he was a hard-working young man, supported by his family.

"He worked at the family cafe but had aspirations to join the police force," said the barrister.

"He was undertaking a college course which would have enabled him to enter the police force once that was passed."

Miss Whittlestone said most of Longstaff's offending happened when he was 16 and that there was a suggestion he had not acted alone.

At the time, she said, he was struggling to fit in with his peer group. Longstaff wept as he was led away to start his sentence.

His name will be on the Sex Offender's Register for a decade, and he will be subject to a Sexual Harm Prevention Order.

Detective Constable Mark Singleton said: “Longstaff was a danger to young girls who he would engage in online conversation with. He demanded nude images from the two victims in this case under a fake profile.

“He caused one of the victims considerable suffering by forwarding the images she had sent him to people she knew.

"He did this out of spite and has shown no remorse for any of his actions. Longstaff attempted to deflect responsibility for his actions onto another party which caused distress to that individual.

“It is important that young people realise the dangers that lurk online as there are people out there who are intent on exploiting children for their own sexual gratification.

“We encourage anyone who has any suspicions of any sort of abuse to contact us so we can investigate."

Stuart Pattinson, a senior prosecutor with the CPS in Cumbria, said: “The CPS and police worked closely to build a compelling case against Cameron Longstaff, demonstrating that he was responsible for collecting indecent images on his computer whilst operating a false identity to blackmail his victims.

"As a result, a jury found him guilty of all the offences he faced.

“I would like to highlight the bravery and resilience of the young victims and witnesses involved in the case, and the outstanding investigation conducted by Cumbria Constabulary which has assisted us in bringing this man to justice.”

The NSPCC has highlighted the sentencing as a reason why it wants the Government to introduce a mandatory code of conduct to create safe accounts for under 18s - with measures including grooming alerts in place.

A spokesman said: "Longstaff manipulated and bullied his young victims into sending intimate images of themselves for his own depraved sexual gratification.

"He then cruelly shared the images of one of the girls with her Facebook friends, putting her through further trauma.

"It is vital that these girls now receive the support they need to move forward."