CNN host Piers Morgan continued to berate gun rights advocates on Wednesday, calling the NRA "cowards" on Twitter.

"I've repeatedly asked the @NRA leaders to come on my show, and they've repeatedly refused. Cowards, the lot of them," the former British tabloid editor tweeted.

Morgan has been on a personal crusade against gun violence since the tragic mass shooting of 20 children in Newtown, Connecticut. He has frequently used his CNN show to call for more gun control laws and argued with gun rights advocates on Twitter. In December, he said the head of the Gun Owners of America (GOA), Larry Pratt, was an "unbelievably stupid man."

His outspoken views have roused the ire of conservatives, many of whom signed a petition asking the White House to deport him "for his effort to undermine the Bill of Rights." In an official statement, the White House said it had no plans to send Morgan back to the United Kingdom.

CNN president Jeff Zucker recently said he supported Morgan's campaign against gun violence.