Mitt Romney escalated his ongoing spat with GOP presidential frontrunner Donald Trump at a Republican dinner Tuesday night in Washington, D.C., poking fun at Trump’s faith and his multiple marriages.

“Donald Trump has had several foreign wives,” Romney reportedly joked at the National Republican Congressional Committee’s annual dinner. “It turns out that there really are jobs Americans won’t do.”

Mitt Romney at @NRCC dinner: “Donald Trump has had several foreign wives. It turns out that there are really are jobs Americans won’t do.” — Kris Hammond (@KrisHammond) March 23, 2016

Trump’s first wife, Ivana, immigrated to the United States from Czechoslovakia. His third wife, Melania, is a former model and jewelry designer from Slovenia.

Romney also knocked Trump for questioning his Mormon faith while campaigning in Utah ahead of Tuesday’s winner-take-all primary, which he lost to Sen. Ted Cruz (R-TX).

“He could have just asked my wives,” Romney quipped.

The two men have been locked in a public feud for weeks, both online and off. Earlier in March, Romney gave a speech imploring Republican voters not to vote for Trump.

“Donald Trump is a phony. A fraud. His promises are as worthless as a degree from Trump University,” Romney said in his nationally televised address at the University of Utah. “He’s playing the American public for suckers.”

Trump fired back at the one-time GOP presidential nominee, saying Romney was “begging” for his endorsement during the 2012 election.

“I could’ve said, ‘Mitt drop to your knees’ and he would’ve dropped to his knees,” Trump told supporters at Maine rally. “He was begging. He was begging me.”

h/t The Hill