"What I would say to Senator McConnell: I know Trump can be a handful, but he is the most dominant figure in the Republican Party", th South Carolina Republican continued.
"Mitch is a dour, sullen, and unsmiling political hack, and if Republican Senators are going to stay with him, they will not win again".
"There's no question, none, that President Trump is practically and morally responsible for provoking the events of the day", McConnell said Saturday, after Trump, the only president to be impeached twice, was acquitted on a 57-43 vote.
A recent poll conducted by Politico-Morning Consult revealed that Trump's popularity within the Republican Party has not decreased even after impeachment trials. This number is the same as the amount of Republicans who wanted to show support to the defeated leader back in November.
However, McConnell said that he could not vote to convict Trump because he was out of office-a position rejected by most legal scholars and numerous nation's founders.
In fact, according to several media accounts, Trump's 622-word diatribe initially included a dig at McConnell having "too many chins and not enough smarts" - before aides persuaded him to drop it. Cartoons and memes that followed the report highlighted Trump's own multiple chins.
After 50 Democratic senators and seven Republicans voted that Trump was guilty - a majority in the 100-seat Senate, but not the two-thirds needed for a conviction - McConnell let loose, excoriating Trump for the attack that saw five people die and the halls of the U.S. legislature ransacked by his supporters.
Mr Trump further blamed Mr McConnell for the party's loss of two Senate seats in a Georgia runoff election on 5 January, handing control of the Senate to Democrats.
The new suit alleges that "on and before January 6, 2021, the defendants. conspired to incite an assembled crowd to march upon and enter the Capitol of the United States for the common goal of disrupting, by the use of force, intimidation, and threat, the approval by Congress of the count of votes cast by members of the Electoral College as required by Article II, Section 1 of the United States Constitution".
"McConnell has no credibility on China because of his family's substantial Chinese business holdings", Mr Trump wrote.
The clash between the current and former GOP leaders comes as the Republican Party at large grapples with warring factions at odds over whether to continue in Trump's likeness or forge a path veering from the former President's legacy.
"If Republican Senators are going to stay with him, they will not win again", he said.
"Where necessary and appropriate, I will back primary rivals who espouse Making America Great Again and our policy of America First".
"This is a big moment for our country", Trump wrote, "and we can not let it pass by using third rate "leaders" to dictate our future".
Meanwhile McConnell came under criticism from Biden for his position on the new administration's $1.9 trillion Covid-19 economic relief bill.
A McConnell spokesperson did not immediately return requests for comment.