Matthew Shanks, who wept throughout his 20-minute hearing, was told by a judge he has caused “immeasurable harm” to his victim – who was aged just six when he first abused her.
Judge Michael Heath told Shanks: “There have to be prison sentences for these offences and they have to be of considerable length.”
Shanks, of Morton Terrace, Gainsborough, admitted six offences of sexual assault on a child under the age of 13.
The 28-year-old also admitted causing or inciting a child to engage in sexual activity and a further charge of engaging in sexual activity in the presence of a child.
He was placed on the sex offenders’ register for life and given an indefinite sexual harm prevention order which bans him from having contact with any child under 16.
Clive Stockwell, prosecuting, said Shanks abused the girl on a number of occasions. He also tried to persuade her to let him photograph her, but she refused.
The offences came to light after the victim disclosed to her family what had happened.
When Shanks discovered the girl’s family had been told of the abuse he wrote a letter to his victim apologising to her.
Mr Stockwell said: “The disclosure by the girl led to his arrest. When he was seen by the police he fully admitted the offences.”
The victim, in a statement read out in court, said she felt disgusted by what Shanks had done to her and said she has since had to have counselling.
Directing her comments at Shanks, she said: “The sobbing and remorsefulness you have shown is only guilt. I will never, ever forgive you for what you have done. Any sentence is temporary for you. Mine is a life-time sentence.”
David Stanton, in mitigation, described Shanks as an immature man who is now disgusted with himself for the way he has behaved.