Oh, no! It’s war between Britney and Cher!

Britney Spears is furious after the aging pop diva made a nasty wisecrack about the pop tart in front of a concert audience in New Zealand recently.

Cher, who is on her worldwide farewell tour, told the crowd: “I’m not going to give up show business but I’m going to give up touring because, you know, there are all of these young girls coming out like Britney.”

When her fans booed loudly at the mention of Britney’s name, Cher snidely remarked, “I know — they are ho’s, aren’t they?”

Now sources say that as far as Britney is concerned, the gloves are off.

According to a source, she told friends, “I wanna know — just who’s the ho, Cher?”

The 23-year-old singer’s spokesperson said about Cher, 58: “For someone who has had their fair share of bad press, it is surprising she would comment on women she hardly knows.”

A source close to Britney told The ENQUIRER: “This dis by Cher has been very upsetting to Britney because she always looked up to and admired Cher. But now she feels she’s been stabbed in the back.

“Britney thinks Cher took a cheap shot at her just for the sake of a laugh . . . and she doesn’t think it’s funny.

“She snorted to a pal, ‘Before she starts calling anyone else a ho, Cher should take a look in the mirror!’ “

Britney is still smarting from Cher’s last-minute cancellation when she was supposed to do a duet with her onstage at the MGM Grand in Las Vegas for an HBO special three years ago.

Spears was quoted as saying at the time: “When they asked me, ‘Who would you like to do a duet with?’ I was, like, ‘Please let’s do it with Cher because I remade “The Beat Goes On.” ‘

“But then when I found out she wasn’t gonna be able to do it, I was really disappointed, but I understand because she’s a busy woman.”

Said the close source: “At the time, Britney gave Cher the benefit of the doubt when she backed out of the gig, even though she was deeply hurt and upset. Now, this is like adding insult to injury. Britney says she’s not just going to get mad . . . she’s going to get even!”

Mark Bego, an author who has written two best-selling books on Cher, told The ENQUIRER: “I think that Britney needs to lighten up a little bit. As far as Cher was concerned, it was just a joke. She feels as if she’s got nothing to lose, so why not start a little controversy?

“She certainly can’t call any other woman a ‘ho’ with a straight face.

“Cher has had so many men over the years that when I wrote the book ‘Cher: If You Believe,’ I had to put in a ‘Boyfriendography.’

“Almost 20 men were listed — and those were just the ones I knew about!”