Speaking to The Sun, 16-year-old Molly Ranger says she dated the singer in August last year.
After they started chatting online, the pair reportedly became serious and Molly unexpectedly fell pregnant.
The teenager claims James, 18, asked her to have an abortion so he could focus on his singing career.
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Molly told the paper: "It was like he didn’t care."
She says the singer ‘ignored’ her when she was rushed to hospital after miscarrying the baby.
She said: “I just cannot believe how cold and evil he has been.”
“I was lying there in agony having a miscarriage, calling him and he didn’t come. That is the one thing I will never understand.
“He told me he loved me and I was losing his child and he just didn’t pick up the phone."
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A source close to James told The Sun: "James is disappointed such a private matter has been discussed publicly.
"He isn't proud of how he handled the situation or what he said to Molly. He realises he should have been more sensitive and supportive but he panicked rather than thinking things through.
"He was only 17 at the time and had only known Molly for a short period of time, so didn't feel mature enough to take on such a big responsibility. He very much regrets the situation he and Molly found themselves in and how he dealt with it."
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