Poor planning by the city’s Department of Education has forced it to return $133 million in unused state pre-kindergarten funds since 2007, an audit has found.

Comptroller John Liu ripped the agency for not seeking new groups to operate state-funded pre-k programs, and for not keeping better track of existing programs’ performance and demand for seats.

This despite the fact that the DOE had committed to better record-keeping back in 2001, based on the findings of an internal task force.

“Eight thousand more kids a year could be in pre-k if the Department of Education would just do its homework,” Liu said.

“It’s hard to understand why the DOE would ignore its own internal recommendations and leave $30 million [the amount of last year’s returned funds] on the table annually.’’

School officials told Liu’s office that seats were hard to fill because the state funds can be used only for half-day programs that appeal to few working parents.