The express buses that carry commuters from the outskirts of the city into its Manhattan center have been tardy, with 30% missing their scheduled departures, according to an audit from city Comptroller Scott Stringer released Thursday.

In a survey of 645 bus runs in fall 2013, only 69% of express buses that left on-time -- the rest had left earlier or later than scheduled.

Staten Island express buses had the worst performance in the audit, with 64% of runs, or 60 buses, leaving on time, the audit reported.

"Working people in this city -- those that are farthest away from the business core -- district rely on these express buses," Stringer said.

Express buses, which cost more to ride than regular buses and have nicer seats, make limited stops on their way through Manhattan. The audit checked a bus' first and last stop in the borough it departs from, as well as its first and last stops in Manhattan, in the morning and afternoon.

Early and late express buses could mean passengers waiting up to 28 minutes for their ride into the city, the audit found.

MTA spokesman Kevin Ortiz dismissed the importance of a bus' adherence to schedules, and that a passenger's wait time at a stop between buses is the better measure.

"Their primary concern is that we have even service, not if specific buses are meeting their scheduled times," Ortiz said. "In addition, there are other extraneous factors such as traffic and road conditions that we unfortunately have no control over."