Phillip Mitchell, 47, of Beechwood Court, Seacroft, pretended to act as a matchmaker between the girl and a non-existent teenage boy to get her to send him indecent text pictures.

He also told his vulnerable victim she had to have sex with him if she wanted her fictional teenage admirer to be interested in her, before launching a drunken sex attack. Mitchell was jailed for eight years after being convicted of causing a person with a mental disorder to engage in sexual activity by deception and assault by penetration on February 6 this year at Leeds Crown Court.

Lord Justice Maurice Kay, Mr Justice Sweeney and Mrs Justice Slade, sitting at London's Criminal Appeal Court, heard him argue that he had been punished too severely.

Mitchell's lawyers claimed his offence had been put in too high a sentencing bracket, more suitable for an offence such as rape.

But Mrs Justice Slade, dismissing his challenge, said Mitchell had carried out "a campaign to groom (his victim) with the aim of taking advantage of her disabilities and having a sexual relationship with her." She also condemned his "sinister campaign" to exploit the "vulnerability of the victim and get her to send him photos of her intimate parts.

"This sentence was not manifestly excessive," the judge concluded.