Former Rep. Patrick Kennedy (D-R.I.) has asked Sen. Scott Brown (R-Mass.) to pull a radio ad off the air that invokes the name of his late father, former Sen. Edward Kennedy (D-Mass.). But Brown's campaign says he won't oblige.

The tiff developing between Brown and the Kennedy family was set off by Brown's support for legislation to allow employers to refuse to cover healthcare services for their employees that they find morally or religiously objectionable. The issue has become a major point of contention between Brown and Elizabeth WarrenElizabeth Ann WarrenRising star Abrams advances in Georgia governor race Progressive rise is good news for Sanders, Warren Juan Williams: Trump gives life to the left MORE, the Democratic front-runner in the race to unseat Brown.

Attempting to couch his support for the exemption in the legacy of Edward Kennedy, the extremely popular former senator and Catholic whose seat Brown now holds, Brown released a radio ad last week invoking his name.

"Like Ted Kennedy before me, I support a conscience exemption in health care for Catholics and other people of faith," Brown says in the ad.

Patrick Kennedy sent Brown a letter Sunday calling Brown's ad "misleading and untrue."

"Providing health care to every American was the work of my father's life. The Blunt Amendment you are supporting is an attack on that cause," Kennedy wrote.

He asked Brown to immediately stop broadcasting the radio ad and not to cite his father in the future.

An aide to Brown told The Hill that the ad will continue to run.

Brown sent a letter back to Kennedy saying he would like to think that if Kennedy's father were alive today, he would work with Brown to find a solution that respected the right of Americans to practice their religion.

"When your father told the Pope in his 2009 letter that he supported a conscience exemption for Catholics in health care, he did not mean to put himself on the opposite side of the church or to suggest that he would force them to accept a situation with which they could not abide," Brown wrote. "And yet, that is exactly the situation we are faced with today."

The situation Brown alluded to stems from a decision by the Obama administration to require employers — including Catholic institutions such as schools and hospitals — to provide free contraception coverage for their employees. Obama later offered an accommodation that shifted the cost of that coverage to insurance companies and away from employers, but that leaves the mandate in place, a decision that did not satisfy some in the religious community.

Patrick Kennedy and others believe the exemption for moral and religious objections that Brown is supporting is overly vague and broad, and could be exploited. But Brown maintained in his letter that similar language was included in legislation from 1995 that Edward Kennedy supported.

—This story was posted at 6:53 p.m. and has been updated.