The city auctioned off a taxi driver’s Crown Victoria yellow cab while he was in a coma after being viciously assaulted on New Year’s Day, a lawsuit claims.

The source of Key Chun Kim’s livelihood was improperly sold for $2,600 six weeks after the beatdown, says the suit filed yesterday in Brooklyn federal court.

Kim’s sister, Kristin, filed the suit on his behalf because he’s still incapacitated from the attack, prompted by a dispute with a passenger over a fare to Brooklyn.

Andrew McElroy, 28, has been arrested and charged with three counts of assault. He has pleaded not guilty.

The cab was tagged as an “abandoned vehicle” by the NYPD, the suit alleges.

Cops say it was a mistake.

“The NYPD mistakenly sold the vehicle at auction,” a police spokesman said, adding that the department fully supports restitution.