is adamant he did not lay a single finger on his ex-girlfriend during an argument back in September ... claiming she's making the whole thing up in a shameless cash grab ... sources close to Busch tell TMZ Sports
As we previously reported, the NASCAR driver is being investigated for an alleged domestic assault on his ex Patricia Driscoll
at Dover International Speedway on the weekend of Sept. 26th.
Sources close to Busch tell us ... the couple had broken up about a week before the incident -- and Busch was surprised when she showed up to his motorhome.
We're told ... Busch acknowledges they got into an argument -- but claims it never got physical.
Sources tell us ... Driscoll has told authorities Busch choked her inside the motorhome.
TMZ Sports spoke with Busch's attorney Rusty Hardin
who tells us, "This allegation is a complete fabrication by a woman who has refused to accept the end of a relationship and Mr. Busch vehemently denies her allegations in every respect."
He adds, "The Dover Police Department has been informed that Mr. Busch will fully cooperate with their investigation and he expects to be vindicated when the entire truth of the situation comes to light."
And there's this -- we're told ... days after the incident, Busch's lawyer was contacted by a person claiming to represent Driscoll looking to negotiate a monetary settlement.
We're told that attorney resigned from representing Driscoll just days later.
We also spoke with police who tell us Driscoll didn't report the alleged assault until Nov. 5th -- six weeks after the incident.
Attempts to contact Driscoll have been unsuccessful.