The pair had been at loggerheads throughout the third episode of the reality show, but things took a turn when events agency owner Waterman-Smith gave her rival “a quick, single push” following a disagreement, when Vana Koutsomitis took Elle Stevenson and Jenny Garbis back to the boardroom.
The catfight happened off-screen on the show, which aired on 21 October.
A source close to the programme said: “The incident was witnessed by several members of Production. Selina pushed Charleine, and at no point did Charleine initiate physical contact with Selina or respond to Selina’s push.”
A spokesperson for The Apprentice said: “The incident, which resulted in Selina being given a verbal warning, was dealt with quickly and professionally. Both women decided to stay in the process after discussions with the production team.
“We take our duty of care to the candidates very seriously and strongly refute any allegations to the contrary.”
However, Waterman-Smith, 31, fired back at Wain on Twitter, writing: “I think it’s pretty obvious by the constant verbal attacks shown in TV who the bully is, not to mention the continued cyber abuse.
“Nobody gave me any warning, I was promised to be separated from her on future tasks and in the house, that was the only reason I stayed.”
“Producers don’t see everything, like snatching, jostling, snide comments and “off camera” things, but they might see self-defense from me.”
Wain, also 31, tweeted back: “Not going to waste my time on false allegations, but would like to state truth always comes out! #selina #apprentice everyone sees through u. Thank u to all producers for stating the truth & for papers publishing with the correct info, truth always reveal.”
Both women had been on the same team for the week’s challenge, which had seen Waterman-Smith, a former podium dancer-turned-events organiser, negotiate for snails by telling the seller a sympathetic story.
A friend of Wain, who served in the Royal Navy for over 11 years, said she was “upset and shocked” by the incident with Waterman-Smith.
“Charleine was completely in shock, she didn’t want to retaliate and make the situation any worse, she took the dignified response and walked away,” they said.
“She spoke at length to both the production team and her husband. Her husband was very supportive and reminded her that it was the opportunity of a lifetime, and she decided she wanted to continue in the process and do her best for herself and her family.
“Although Charleine was upset by the situation, after talking to the production team about the incident she decided she was comfortable with them both continuing in the process, which was very gracious of her. She wanted to put the incident behind her and focus on doing well in the tasks at hand.”
The Apprentice continues on BBC1 on Wednesdays.