Leigh McMillan, 46, from Milton Keynes, groomed the child with cigarettes and drugs before subjecting her to the abuse during the mid-1990s.
McMillan attacked the schoolgirl on her mother’s bed and warned her not to tell on him.
He assaulted her around 100 times, the court heard.
McMillan is a lead figure in the EDL’s most unwanted ‘Lee Rigby’ campaign – a campaign to use the soldier’s death for further hatred.
A judge at the Old Bailey sentenced him on Monday to 17 years behind bars.
A representative from the Hope Not Hate Campaign, set up to fight fascism, was in court to witness his downfall.
“He seemed really embarrassed and looked ashamed He normally comes across as cocky when he speaking for the EDL, so this was quite a difference,” he said.
Hope Not Hate describe McMillan as a leading figure in the far right movement.
They say groups he has been affiliated with have been quick to criticise Muslims over child abuse following high profile cases of Asian grooming gangs.
But McMillan’s own arrest and conviction caused red-faces among his colleagues, claim Hope Not Hate.
“Members of far group groups have tried to hush it up,” said the spokesman.
It is alleged one far right campaigner wrote on Twitter: “We don’t want the left rubbing our noses in the dirt pretending they are whiter than white ourselves.”
Hope Not Hate was founded in 2004 to provide a “positive antidote to the politics of hate”. It helps expose illegal activities of extremists.