Trump in Cleveland on Thursday for the first official prime-time Republican presidential debate of the 2016 US presidential campaign. REUTERS/Brian Snyder Donald Trump is all but accusing a top Republican pollster of trying to shake him down.

After the presidential debate on Thursday night, Fox News featured a focus group conducted by Frank Luntz that utterly slammed Trump. On Monday, Trump told Business Insider that he thought he was panned by Luntz's group because he declined to hire Luntz's research firm.

"This has been going on, he's putting the arm on me all the time, and then he does these polls that are totally in violation of every other poll that was done," Trump said of Luntz.

Trump said post-debate polls that show he remains ahead of the GOP field prove the focus group was wrong. He further described Luntz, a regular contributor to Fox News and one of the country's best-known conservative consultants, as "unfair" and "terrible."

"I watch this guy do a really negative report on me, and the only reason he did it, in my opinion, is because I didn't want to hire him commercially," Trump said of Luntz. "I think it's disgusting ... I think he uses his power at Fox to maybe — to get work."

In a phone call with Business Insider, Luntz vehemently denied Trump's accusation.

"You've got to understand that I don't care who wins and loses — I only care that I'm accurate," Luntz said. "Even if I say things that candidates don't like, I don't expect them to take it personally. I don't expect them to launch World War III."

Luntz said Trump "launches an attack on everyone who is even remotely critical." He also suggested Trump would probably be praising him if the Fox News focus group gave him a good review.

"If the group had said Donald Trump won this debate ... I would be the world's greatest pollster," Luntz said. "Because it didn't, I'm not."

Trump provided Business Insider with copies of multiple emails in which he said Luntz's assistant asked to set up meetings with him.

"He called me incessantly to meet with me. Finally, I said, 'Look, let's get rid of this guy,'" Trump said of Luntz. "He's on a lot of television programs, I guess I've got to see him. And he wanted me to hire him on a commercial basis, meaning hire him to work on various — you know, you see, I have many companies."

Trump said he rejected Luntz's pitch.

"I said, 'Frank, when I make deals I make them myself," Trump said. "I don't need focus groups or whatever it is you do.' I said, 'Frank, if you were so good at this, you'd be me.'"

Trump had one of his executive assistants, Katie, forward Business Insider the emails he said he received from Luntz's office. During the phone call, Trump praised Katie for quickly recovering the messages.

"She's beautiful and she's smart," Trump said of his assistant.

Frank Luntz. AP The first email provided by Trump's office was dated May 22. In it, Luntz's assistant asked to set up a meeting for Luntz with Trump and one of his marketing executives.

"Frank will be in NY on Monday June 1 and would love to meet with Mr. Trump and Amanda Miller should their schedules allow," Luntz's assistant wrote, adding, "If you could kindly let me know if a meeting is possible I would be greatly appreciative."

The second email provided by Trump's office was dated July 8.

In that message, Luntz's assistant referred to an article about a speech by Trump in California that was scheduled to take place the next day. The assistant said Luntz would be in the area "at the same time" and "would love to have a brief meeting" with Trump "before or after the event." Another email showed Luntz's assistant following up on July 9 after not receiving any response and again asking "if Mr. Trump's schedule allows for a brief meeting with Frank."

Luntz, however, said it was actually Trump who asked for the meetings. He also said he had met with all of the major Republican candidates who participated in last week's prime-time debate.

"He invited me to come see him in New York," Luntz said of Trump. "I talk to every presidential candidate. I talked to every single person on that stage ... He's no different."

Luntz said he requested the meeting in California when he realized Trump's event was "right across the street" from his house.

"I wanted to show him my home," Luntz said.

Luntz pointed out that an NBC News online poll conducted Friday echoed his focus group and showed 29% of people felt Trump had the worst performance of the debate. He described Trump's reaction to his focus group as "unprecedented" for a White House hopeful.

"This guy has got considerable support, and he's going to have considerable support all the way through," Luntz said of Trump. "He's also got considerable enemies, and he doesn't like it when anyone says that he's not great."

Luntz also attacked Trump's habit of bragging about the crowds he attracts on the campaign trail.

"He says to me that he got more standing ovations than anyone up in New Hampshire," Luntz said. "He didn't. He says he got a bigger standing ovation than anyone in Iowa. He didn't. These are factual inaccuracies that are surprising for a presidential candidate."

Trump at the 2015 FreedomFest in Las Vegas on July 11. REUTERS/L.E. Baskow Luntz added that he regretted "ever contacting" Trump.

"I absolutely acknowledge I went to see him," Luntz said of Trump. "I absolutely acknowledge I invited him over to my house. He just takes everything and he twists and turns and it's kind of sad. Anyone who challenges him gets this sort of treatment."

Luntz declined to provide Business Insider with emails showing how his meetings with Trump were set up. He said, however, that Trump's initial request for a meeting took place at a political event in New Hampshire and was witnessed by several people.

"It became a joke in New Hampshire because I was supposed to meet with Mike Huckabee," Luntz said. "I was trying to decide, 'Can I do this or not?' ... It was his invitation."

Luntz's focus group isn't the only aspect of Fox News' handling of the debate that has been criticized by Trump and his team. Trump has spent the past several days attacking one of the moderators, Megyn Kelly, for some of the questions she threw at him during the debate. Michael Cohen, who is special counsel to Trump, has said he believes Luntz's focus group was a "total setup" and that Fox News' debate coverage was part of an "organized attack."

According to Trump, Fox News head Roger Ailes called him on Monday morning and assured him he would be treated "fairly" on the network. Trump told Business Insider he did not discuss Luntz with Ailes.

"Roger's a great guy," Trump said. "I think this is Frank. I don't think this has anything to do with Fox. I think Frank uses Fox, but this has nothing to do with Fox. This is Frank Luntz."

Trump said he saw Luntz's focus group while he was flying home from the debate. He said he was immediately shocked because polls that appeared on the websites of Time and The Drudge Report had declared him the winner.

Trump with his daughter Ivanka. Jamie McCarthy/Getty Images "So, I win the debate and I go, I'm actually on my plane heading back, and I see Frank Luntz is on television," Trump recounted. "He's knocking the hell out of me with these people. I said, 'Who are these people?' They can't be representative, because while I'm on the plane, my daughter is coming up to me, Ivanka, saying, 'Dad you just — you're killing them in the Drudge ... You're killing them in Drudge. You're killing them in the Time magazine poll.'"

Trump said he was also sure of his victory because several of his rivals told him he beat them.

"Four of the candidates came up to me and said, 'You crushed it tonight. You won,'" Trump said.

Trump declined to name the candidates who told him he won the debate.

"I can't tell you that because I don't want to embarrass them," Trump said. "They were very nice to say it."