A web pervert who disguised himself as a girl and tricked children into performing sex acts has had his jail sentence increased.

Francis Knight, 31, of Portsmouth, used Facebook to trawl profiles of youngsters and then make contact with his victims by pretending he was female.

He reached out to 200 youngsters and began grooming potential victims before luring a number of boys under 13 years old to perform obscene acts on a webcam.

He then took pictures of the scenes described in Portsmouth Crown Court as "appalling acts". Victims were left feeling "sick and angry" when they discovered they had been conned, said a judge.

Knight's sentence was more than doubled from 16 months to four years by the three judges. They called the original tariff unduly lenient after being asked to review the sentence by the attorney-general.

Knight was convicted of inciting children to engage in sexual activities and making indecent photographs of children.

Solicitor-general Oliver Heald said: "The actions of Francis Knight were appalling.

"He posed as a teenage girl online to gain the trust of young boys and then exploited them for his own gratification.

"Child sexual offences like these are very serious and can be difficult to detect because the culprits may never be seen by the victims and they do not use their real names."

Judges Lady Justice Rafferty, Mr Justice Griffith Williams and Mrs Justice Thirlwall read impact statements by victims whom Knight groomed and exploited.

Rafferty said: "In victim impact statements and other means of expression, many victims reported feeling bad, scared, sick and angry."