Cathriona White's mother has accused Jim Carrey of hiring a private detective to "dig up dirt" on them in his fight against their wrongful death lawsuit.
Irish makeup artist Cathriona had been dating Carrey on and off since 2013 and she took her own life in September 2015.
Her mother Brigid Sweetman lodged the suit earlier this week, saying Carrey should be "ashamed" of his treatment of her daughter, amid claims he illegally provided White with prescription drugs involved in her suicide.
Ms Sweetman repeats allegations previously made by White's estranged husband Mark Burton that the Dumb and Dumber star gave her daughter three sexually transmitted diseases before her death - two cases of herpes and chlamydia.
Carrey vehemently denies ever having either.
White took her own life in September 2015 by overdosing on a cocktail of Ambien, Propranolol and Percocet. They had been prescribed to Arthur King, the pseudonym Carrey used to obtain his medicine.
Lawyers working for Sweetman said on Thursday that a "number" of the family's friends said they had been approached by former LAPD detectives.
Attorney Michael Avenatti told DailyMail.com: "How dare Carrey and his Hollywood lawyers try and malign the family and intimidate them," the lawyers said.
"Sending private investigators out to dig up dirt on a grieving mother is disgusting. These people have no bounds."
In the lawsuit, Sweetman claims that he tested positive for sexual transmitted diseases in a test taken on January 28, 2013 under a false name.
"Jim Carrey and his attorney have told the world that Carrey has never had STDs and he has never tested positive for STDs. They have called me and Mark 'shams' for claiming otherwise," she wrote in a new statement.
"I am demanding they immediately release the full 2013 lab results so people can judge for themselves who is telling the truth and who is lying.
"If they publicly release and publish the full Quest Diagnostics lab report for the blood sample Carrey gave on January 28, 2013 at 11:40am under the name Jose Lopez and if it shows Carrey did not test positive for STDs, I will immediately dismiss the case and apologise."
Referring to a note left by Ms White, in which she described being called a "whore" and "an opportunist", Ms Sweetman added: "Every mother and father that has a daughter should read Cat's handwritten letter to Jim and decide for themselves what kind of guy he really is."
In papers filed with the Los Angeles Superior Court, Ms Sweetman is suing Carrey for wrongful death and violation of the Drug Dealer Liability Act.
In response to Ms Sweetman's lawsuit, Carrey's lawyer said: "It is understandable that a mother who has lost a daughter will look for someone to blame.
"But in directing her grief and rage at Jim Carrey and joining this ridiculous attempt to capitalise on Cathriona's suicide, Ms Sweetman is heading down the same dark path as Cathriona's green-card 'husband' Mark Burton."
He has denied any involvement in supplying drugs to Ms White.
"It would be easy for me to get in a back room with this man's lawyer and make this go away, but there are some moments in life when you have to stand up and defend your honour against the evil in this world," he said.
"I will not tolerate this heartless attempt to exploit me or the woman I loved. Cat's troubles were born long before I met her and sadly her tragic end was beyond anyone's control.
"I really hope that some day soon people will stop trying to profit from this and let her rest in peace."
In an interview with US website TMZ Carrey's lawyer Marty Singer claimed his client never gave White a single pill.
Singer called the lawsuit "a money-grab scheme".
Lawyers for the Hollywood star have previously said that the allegations against him are "bogus" and "categorically disputed".
During her time in Los Angeles, Cathriona was carving out a successful career in film and TV, had taken classes at Scientology's Hollywood Celebrity Centre.
In 2013 she married fellow scientologist and cameraman Mark Burton. The couple had met while working on an online comedy series.
Cathriona's ex-husband Mr Burton, in his lawsuit against Carrey, has claimed the actor used his "immense wealth and celebrity status" to access prescription drugs that caused Cathriona's death.
It is also alleged that Carrey or his assistants monitored the 30-year-old's movements from her house through surveillance cameras, but they failed to report that Cathriona hadn't left the house in more than a day.
Speaking previously about Mr Burton's lawsuit, Carrey had commented: "I will not tolerate this heartless attempt to exploit me or the woman I loved.
"Cat's troubles were born long before I met her."