ASHTON KUTCHER is following in Charlie Sheen’s footsteps – by disrupting the set of “Two and a Half Men,” sources say.

Now in his second season on the CBS sitcom, the 34-year-old actor has grown increasingly surly as the show’s ratings slide, according to the sources.

“When Ashton joined the cast, he was like a breath of fresh air,” said an insider. “He was seen as the show’s savior, and everyone rallied around him.

“But it’s pretty clear Ashton is not as enthused about ‘Men’ as he was last season. Some people are even calling him ‘Charlie Jr.’ behind his back.”

The sitcom’s ratings surged when Ashton’s character, dot-com billionaire Walden Schmidt, replaced Sheen’s bad-boy jingle writer Charlie Harper. But since the new season began, the ratings have been dropping. “That’s left Ashton complaining about everything from the scripts to the makeup and even costume choices,” said the insider.

The bad blood spilled over to the recent Emmy Awards, when Kutcher’s co-star Jon Cryer won for best actor in a comedy and failed to mention Ashton in his acceptance speech, sources say.

“Ashton was peeved he wasn’t nominated, and he let everyone know about it,” revealed the insider. “So Jon saw no need to kiss up to him.”

Kutcher – who’s now dating his former “That ’70s Show” co-star Mila Kunis – is also said to be unhappy that he’s only getting $700,000 per episode, not the $1 million he wanted.

“Ashton feels he’s being underval­ued,” explained the source. “At this point, I think it’s doubtful that he’ll return next season.”