'Real Housewives of Beverly Hills' star Dorit Kemsley says her ex-husband owes her child support ... claiming she is their kids' primary caregiver ... while he only has them 5% of the time, TMZ has learned.

In legal docs filed by Dorit's powerhouse attorney, Samantha Spector, the RHOBH star slams PK's recent claims that she's spending crazy on fashion and travel, while ignoring mortgage payments. She claims he is the one dropping serious cash on personal expenses, while not paying bills.

In her filing, Dorit claims she bears the day-to-day responsibility for caring for their two minor kids, who are "in her custodial care 95% of the time without spousal or child support." 

Dorit asked the court to deny PK's request to sell off the home she lives in with their kids … claiming PK's claims that the home is in danger of being foreclosed on are nonsense, since he has more than enough in the bank to catch them up on payments.

For his part, PK claims Dorit has spent over $1 million on luxury clothes and trips around the world, while not making payments on their marital home. He alleged she earns more than him and he has paid the bills -- despite moving out several months ago -- for long enough.

He also claims Dorit has repeatedly left the kids with nannies or her parents, instead of giving him the chance to see the kids.

In recent docs, PK called out Dorit for leaving their kids with their grandparents in Florida, while going to Paris for a fancy birthday getaway.