O’Neill told reporters at his post-match press conference that he had been told that personnel from the Newcastle camp had visited referee Mike Dean’s changing room at half-time of their 1-1 draw, although his claim was vehemently denied by the Magpies.
He spoke out as he addressed the sending off of skipper Lee Cattermole after the final whistle and suggested that the half-time events had contributed to his dismissal, which followed the second-half red card shown to Stephane Sessegnon for violent conduct.
“The referee said he had sent Lee Cattermole for foul and abusive language towards the referee," he said. "It must have been coming up towards the tunnel.
“I don’t think you can be doing that sort of thing. You should leave that to me if that’s the case. But possibly in mitigation we had heard that some of their staff had visited the referees’ changing room at half-time.
“Of course we are not party to what was said. Lee’s mitigating circumstance was that a lot of decisions had gone Newcastle’s way in the second half. That may well be but that doesn’t necessarily mean I agree with it.
“But if you look back at it I think Newcastle can count themselves lucky to have 11 men still on the field at the end if the referee is continuing to play according to the way he started the game.
“It is unfair for me to make an assessment on what was said so I really don’t know but if a referee allows someone to come in and speak to you then that is his prerogative.
“I have no complaints about the [Sessegnon] sending-off. I have seen it back briefly. He raised his arm. He was stupid and I could not be more disappointed.”
O’Neill seemed certain to be celebrating victory until stoppage time when Shola Ameobi cancelled out a first-half penalty from on-loan Arsenal striker Nicklas Bendtner.
“It is two points that have slipped through our fingers but I am very proud of the team,” O’Neill added. “It was a fantastic effort. We looked very dangerous in the first half and probably deserved the lead and we were causing them all sorts of problems.
“The [Sessegnon] sending-off offence put us on the back foot, we knew. We knew we would be under pressure. Newcastle started the second half well but we were weathering that pressure and that was he pivotal moment of the game.
“We had a great chance to make it 2-0 early in the second half and it would have been a long way back for Newcastle. They cleared off the line and that gave them great hope.
“They were never going to give up but we were coping admirably even with the ten men with anything thrown into the penalty box. I am delighted with the team.
"We had a lot to make up for after last week’s debacle at West Brom and we played very strongly. Had we held out we would have deserved all three points.”
O’Neill played down a series of touchline spats with Newcastle counterpart Alan Pardew as tension rose between the two benches.
“In a perverse way I was enjoying it," he concluded. "The noise was deafening. It really was something."