A spokesperson confirmed the news, saying, "It is true that they are expecting a baby, they are over the moon."
Speculation that Emily, 23, was pregnant started when Peter, 40, was seen placing his hand on her stomach at an event in June.
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The couple have been together for around a year after meeting through Emily's father, a doctor who performed surgery on Peter in 2010.
The baby will be Peter's third child – he already has son Junior, eight, and five-year-old daughter Princess with ex-wife Katie Price.
Katie, who recently married Kieran Hayler, is currently around six months pregnant with her fourth child.
A source close to the couple spoke about their happy news, saying, "Peter and Emily absolutely adore each other, so having a baby together feels completely natural.
"They have only been together for over a year, but they were friends for a long time before that. Emily's dad is a surgeon and he operated on Peter when he had kidney stones in 2010.
"Peter became very close to him and his family and his relationship with Emily developed from there. As far as they are concerned they are going to spend the rest of their lives together and will definitely get married in the next year or so.
"Emily has just finished her degree at Bristol University and has passed all her exams. She still wants to have a career as a doctor, so it is very unlikely that she will be a stay-at-home mum."