Meghan Markle may soon be hit with another bombshell amid Megxit — her estranged dad will likely be a key witness against her in an upcoming court case, legal papers reveal.

The Duchess of Sussex, 38, is suing the Mail on Sunday newspaper in the UK for printing a letter she wrote to her father, Thomas Markle, for not attending her May 2018 royal wedding to Prince Harry.

Her 75-year-old father now plans to be the key witness testifying on behalf of the paper, according to new documents filed in London’s High Court.

Potentially adding to the PR nightmare he has already caused his daughter, Thomas Markle will help prove that the Duchess was behind a smear campaign against him in the run-up to her wedding, the documents claim.

Her father has already provided the paper’s lawyers with a series of text messages he says were exchanged in early 2018 as rumors swirled over whether he would be present for his daughter’s big day.

They include one that appears to be an angry exchange with Prince Harry when the Markle claimed he was rushed to a hospital for emergency heart surgery and could not fly to the UK on health grounds, the Daily Mail said, citing the court filings.

“I’ve done nothing to hurt you Meghan or anyone else,” the dad wrote, according to the report. “I’m sorry my heart attack is … any inconvenience for you.”

The letter was the only communication the Duchess has had with her dad since he failed to show at her wedding, the Mail claimed.

The Duchess accuses the newspaper of copyright infringement, misuse of private information and violating the UK’s data protection law by publishing her letter.

The paper insists in court filings, however, that her father “had a weighty right to tell his version of what had happened between himself and his daughter, including the contents of the letter.”

Her father says he only released the letter to highlight the misleading, one-sided picture his daughter was painting about their broken relationship, according to the reports.

If the case goes before a judge, the Mail said it would ask for Meghan to hand over all communications in which she had “caused or permitted her friends to provide information about her to the media or to seek to influence what is published about her.”

The paper also argues that royals “generate and rely on publicity about themselves and their lives in order to maintain the privileged positions they hold and to promote themselves,” according to the docs.

The Sussexes have said they will fund the legal proceedings privately, the Mail said.

The legal development comes in the middle of the Megxit firestorm, with the Duchess reportedly the one pushing to quit the royal family because it was “not working” for her, leaving Harry “heartbroken.”

Meghan was spotted in Canada Tuesday for the first time since the crisis began for a visit at the Downtown Eastside Women’s Centre in Vancouver to discuss issues affecting women in one of the city’s poorest neighborhoods.

With Post wires