Cops let a popular Long Island deli owner off the hook after he drunkenly careened into a fence and a parked car — but their mercy only freed him to be killed in a second DWI crash a half-hour later, a new lawsuit claims.

Cops drove Peter Fedden home after the first incident because he gave the boys in blue big discounts at his popular eatery, Commack Breakfast, his mother’s $30 million lawsuit claims.

Instead of locking him up, Suffolk County cops simply took Peter to his Commack home, his mom, Kathi, alleges.

And once there, Peter switched cars and drove away 30 minutes later, fatally ramming into a building in Hauppauge.

Fedden was extricated from the car and airlifted to Stony Brook University Medical Center, where he died.

He drank two 16-ounce mixed whiskey drinks at a Ruby Tuesday and smoked marijuana just before the initial accident, according to the suit.

He left the restaurant with a female bartender and another customer in his car.

Fedden soon lost control of the vehicle and skidded across lawns, crashed through a fence, and hit a parked car before his vehicle came to rest, the suit claims.

At least seven cops arrived at the scene — but eventually drove Fedden home instead of arresting him for drunken driving, according to the suit.

Fedden knew the officers who responded to the call — and routinely allowed them to eat and drink whatever they wanted at his deli for only a dollar, according to court papers.

Fedden’s mother is suing the Suffolk County Police Department for not arresting him after the first crash and preventing him from driving later that night.

The department did not comment.