Maccarinelli, who was seeking to get his career back on track after serving a six-month ban for failing a random drugs test, came under pressure from McKenzie but did not appear to be in major trouble.
Yet referee Ian John-Lewis saw it differently and stepped in to deny the Welshman the only belt missing from his collection.
"I am absolutely devastated," Maccarinelli said. "The referee apologised to me afterwards.
"We knew he [McKenzie] was strong but it was my plan to take the shots on the ropes. My hands were up and I blocked his shots until the referee stepped in."
Victory for McKenzie was his second successive defence of the title he won in November last year against Jeff Evans.
"It's not my fault, there's nothing I can do," McKenzie said. "I will give this guy a rematch anytime. The fight could have carried on, I can't lie about that."
Ricky Hatton said on Twitter: "Poor Enzo, and poor Ian John-Lewis, outstanding referee, one of the best and I think he knew straight away he jumped the gun."
In the night's final bout, Paul Butler claimed the vacant British super flyweight title with victory over John Donnelly.
Butler stopped Donnelly in the first round with a devastating body shot to delight his hometown fans inside the arena.