TOM CRUISE is worried about his teenage son Connor because the up-and-coming club DJ has become best buddies with hard-partying British actor Alex Pettyfer, a source says.

As The ENQUIRER has reported, 23-year-old Pettyfer – who shot to fame in the raunchy male strip­per hit “Magic Mike” – has a reputation for being vulgar and ill-tempered.

Sources say Cruise fears those badboy antics will rub off on 18-year-old Connor.

“Tom is a hands-on dad, and he’s begging Connor to replace Alex with more respectable friends,” disclosed an insider.

“Connor hasn’t gotten into any serious trouble yet, but Tom lives in fear that his son is one step away from an embarrassing scandal.”

But Connor – a regular fixture on the club scene who recently released his first dance music single, “Closer to Heaven” – has al­ready shifted into the fast lane, said the source.

“He’s smoking ciga­rettes, courting hot models and partying into the wee hours of the morning,” revealed the source.

“It’s definitely not the lifestyle a squeaky-clean guy like Tom Cruise ap­proves of for his son. Tom is very close with Connor and supports his career, but he’s warning him that Alex is liable to pull him down.”

And that influence was evident on Oct. 22 during a video game launch party at the L.A. hotspot Greystone Manor. A huge bottle of vodka was parked on the VIP table that Connor shared with Alex, who stars in the upcom­ing “Endless Love” remake.

The two buds were also said to have partied hearty at the Coachella Valley Music and Arts Festival last April.

Adding to Tom’s concerns is a warning from former Scientologist Lisa Marie Presley. Her daughter, actress Riley Keough, got engaged to Alex in March 2012, just six months after they started dating.

Lisa Marie urged Riley to dump Alex after reports surfaced that he cheated on her. She also feared Alex was just looking to get a chunk of the family’s estimated $300 million fortune.

 Riley broke off the engage­ment, but the two were spotted holding hands in August.

Meanwhile, Connor’s 20-year-old sister Isabella – adopted, like Connor, by Tom and ex-wife Nicole Kidman – is also giving her dad headaches, sources say.

The tattooed art student has sported a rainbow of hair colors, and she briefly lived near L.A.’s seedy Skid Row.

“Tom’s worst nightmare would be having one of his kids go down the same path as Lindsay Lohan or Miley Cyrus,” said the source.

“He’s crossing his fingers that Connor gives Alex the heave-ho.”