The former EastEnders actress will star as Carol Barry, the head of a Liverpudlian criminal family in the BBC drama.
Carol's husband is currently in prison, leaving her as the lone parent of three unruly children - Barry (Carl Au) and daughters Dynasty and Kacey (Abby Mavers and Brogan Ellis).
Lucker spoke of her surprise upon being told that her character had to hit her children, as it is something she would never do in real life.
"When I read that I was going to hit my son I was pretty shocked, as it is not something I could ever do as a mum," she told The Sun.
"Carol is physical with her kids, she is threatening, feisty and angry. She is a very hard woman.
"I couldn't actually hit the actor in real life, but when he saw the power behind my punch, I think he was really grateful I hadn't hit him across the face for real!
"It is very difficult to get to that stage in your head where it is OK to physically hurt someone. I have to take myself off into a corner and psyche myself up, before giving it as much as I can."
The former Footballers' Wives actress said that she is very different from her on-screen roles, saying: "Everyone thinks I'm hard, feisty and angry because of the characters that I have played.
"I'm nothing like that at all. I worry about everything and I'm a real pushover in comparison.
"I am more drawn to those roles though, as they are really meaty parts and it is the way people have come to see me."
She revealed that she was nervous about her first day on the Waterloo Road set. "Growing up, there were a few people around me with that hard edge to their character," she said.
"When I read the part it felt familiar to me. Although I didn't base Carol on anyone, it is inspired by a couple of mums that I knew when I was younger.
"I do have an element of sympathy for Carol because even though she does behave quite appallingly a lot of the time, she has been left to look after three wayward kids when her husband is banged up for armed robbery."
She added: "Carol is not glamorous, she looks very hard. It was a real contrast to the floaty big blonde hair of Vanessa Gold and the white suits.
"She is very uniform with her hair always scraped back, with the same jewellery and jacket on.
"Carol alternates her top but that is about it. It was a choice - I felt this was a woman who, back in the day, would have taken a lot of care of herself but these days it is a practical thing."
Waterloo Road is back on screen in January and the full spoiler for its return episode can be found here.