The Coronation Street star told Sammy Milewski, 25, that he was single when they met in a Barnsley nightclub and the pair went on to spend the night together.
However, when the Rotherham promotions girl discovered she was pregnant Shepherd turned his back on her and said the baby would "ruin his life", the News Of The World claims.
Lauren Shippey - Shepherd's parter of 8 years and the mother of his 1-year-old daughter Nyla - told him to pack his bags as soon as he confessed to the infidelity.
The 22-year-old, who plays David Platt on the ITV1 soap, came clean after Corrie bosses warned him that the story was going to break. A spokeswoman said it was a "personal situation which Jack is dealing with".