Williamson was accused by his manager John Carver of fouling City striker Jamie Vardy to earn his second yellow card, and therefore marching orders.
Carver was furious after the final whistle at the King Power Stadium, with Williamson the prime target of his ire.
“I thought he meant it,” Carver said. “When the ball went onto that left-hand side, my first reaction, five yards before making the tackle was, ‘Don’t do it’ – and he did it.
“Vardy was off the pitch, Willo was off the pitch, the ball was off the pitch. There was no need to do it. I am not accepting that, especially in the situation we are in.”
Asked why Williamson might have done something like that on purpose, Carver said: “I don’t really know. It was just my thought when it happened. I thought he meant that and I have told him so.
“I have actually said this to his face.”
But Williamson issued a statement on Sunday afternoon in which he admitted his tackle was ill-judged, but he insisted that he had not tried to get himself sent off.
???I would like to take this opportunity to apologise to the Newcastle United supporters and my fellow teammates for getting sent-off during yesterday???s game [v Leicester City].
???There was absolutely no intent to hurt Jamie [Vardy] or get sent-off, but I recognise that I should have been more composed and measured in my determination to win the ball.?? Unfortunately, it did the one thing that I never wanted to do, and that was to hurt the team.
???Moving forward, I will do whatever I can to help my teammates prepare for the next two games and fight to get back into the team when I???m next available.
???I???ve had the honour to play for Newcastle United for five years now, and I can genuinely say that I feel privileged to play for this football club.?? I would never do anything intentionally to hurt the team or its supporters.???