An RFU panel met on Sunday to decide Hartley's fate, and gave the player an 11-week ban, ruling him out of the Lions tour to Australia. Ireland's Rory Best is expected to replace him in the squad.
The incident, at the end of the first half in front of almost 82,000 fans at Twickenham, was the first red card in a Premiership final but Hartley has claimed his expletive-led accusation was aimed at Tom Youngs, his opposite number and rival for the Lions jersey, and not referee Wayne Barnes.
The RFU did not accept his explanation, however.
Hartley had already been warned by Barnes for speaking out of turn. Clearly audible on the "reflink" devices available to all fans in the ground, Barnes said that a repeat of any abuse he felt to be aimed at him would lead to "further action" and told the New Zealand-born hooker he was not behaving like a captain.
Five minutes later there was a confusing spell when Northampton fly-half Stephen Myler kicked directly into touch to try to bring the half to a close, despite being told clearly by Barnes, three times, that he could not do so.
A scrum ensued, which led to a Leicester penalty. As the players disentangled Hartley delivered the key "f****** cheat" phrase, and was immediately red-carded.
Barnes then spoke to Tom Wood, who assumed the captaincy, telling the England flanker: "He called me a cheat and he leaves the field."
Down to 14 men against the pre-match favourites, Northampton fought back impressively in the second half, scoring two excellent tries, but they eventually succumbed and Leicester took their 10th title.
Hartley now almost certainly faces a ban that will rob him of his place with the Lions, who fly to Hong Kong on Monday ahead of their three-test tour of Australia.
However, Northampton coach Jim Mallinder claimed the abusive outburst had not been aimed at the referee, giving Hartley a glimmer of hope at his disciplinary hearing, which could be convened as early as Sunday.
"I asked Dylan at half-time and again just now and he said he was talking to Tom Youngs," Mallinder told reporters.
"If you talk like that to another player you wouldn't expect that to happen. Wayne believed he'd spoken to him but if Dylan says he was talking to the player on the floor then I support what he says.
"He said a number of the senior players who were around him agreed that he was looking down and talking to Tom Youngs.
"There will be a hearing and they'll see whether they believe him or not."
The minimum ban for abusing an official is six weeks, ruling Hartley out of Lions contention, and he is unlikely to earn much of a reprieve for previous good behaviour.
He was given a two-week ban earlier this season for striking Rory Best, having served eight weeks for biting last year. Six years ago he was given a 26-week ban for eye-gouging which ruled him out of the 2007 World Cup.
"He's the heartbeat of our club," Wood said. "He wears his heart on his sleeve, he plays on the edge that's what makes Dylan Dylan."
Leicester coach Richard Cockerill, one of the fiercest and most verbal hookers ever to take the field, had little sympathy.
"We spoke all week about discipline and yellow cards, we know Barnes likes to be treated with respect," he said.
"He's a very experienced referee and there's enough history between Leicester and Northampton to know that you have to keep control."
Cockerill was more concerned about the failure to punish Courtney Lawes for the first of two tackles that virtually folded Leicester fly-half Toby Flood in two and ended his involvement after 24 minutes.
"Surely you need to go to TMO (TV match official)?" he said. "It's late and foul play, its a penalty, for me that's a yellow card or potentially more. Is it ok to hit players late and have them leave the field concussed?
"I'm disappointed that we're talking about these things because after coming here and losing a few times this is a great victory."