Christine O'Donnell, the Tea Party favourite and failed Republican Senate candidate, has done little to diminish a reputation for occasionally eccentric behaviour by walking off the set of Piers Morgan's CNN show mid-interview after being gently quizzed about her views on gay marriage.

O'Donnell, who was soundly beaten in November's election in Delaware, in part after old TV footage surfaced in which she talked about dabbling in witchcraft and condemned masturbation, cut short her appearance on Piers Morgan Tonight when the host asked for her views on gay marriage, an issue about which she has previously spoken.

She refused to discuss the subject, even while conceding that it was covered in Troublemaker, the book O'Donnell was promoting on the show.

"You're borderline being a little bit rude," O'Donnell told Morgan when he pressed her on her refusal to address gay marriage. "I don't think it's relevant. It's not a topic I choose to embrace. It's not what I'm championing right now."

Morgan said he was "baffled" at her stance, explaining: "I'm just asking questions based on your own public statements, and now what you've written in your own book."

Asked whether she supported the argument of fellow Tea Party Republican Michelle Bachmann that the US military should reinstate a ban on openly gay service personnel, O'Donnell answered: "I'm not talking about policies. I'm not running for office. Ask Michele Bachmann what she thinks."

She went on to suggest that as a courteous talkshow host Morgan should only cover subject areas his interviewees wanted to discuss. After an incredulous Morgan rejected this, O'Donnell, being interviewed in a separate studio, appeared to look towards an off-camera aide for instructions. "OK, I'm being pulled away," she said, beginning to remove her earpiece.

"I was supposed to be speaking at the Republican Women's Club at six, and I chose to be a little late for that," she said, "not to endure a rude talkshow host, but to talk to you about my book and the issues I address in my book."

O'Donnell's book, which she hopes will become a Tea Party bible, is her attempt at political rehabilitation after a disastrous Senate bid, which included a campaign TV ad that opened with the much-mocked line: "I'm not a witch."

Before walking off Morgan's show, O'Donnell admitted the ad had been a mistake: "I listened to the so-called experts who have been losing election after election. The experts aren't always experts."

Morgan, meanwhile, remained apparently baffled, retweeting to his 1.1 million followers a journalist's tweet saying: "Christine O'Donnell is the first author in the history of publishing to walk out of a TV interview because the host apparently read her book."