Police are searching for a group of "idiots" who "graffiti-bombed" an Auckland train with passengers trapped inside.

Commuters watched helplessly from inside the train as the group caused $20,000 of damage in mere minutes.

The emergency brake was pulled to stop the train at the Meadowbank station at 7am on February 24. Police released CCTV footage of the graffiti attack last night.

"These idiots caused approximately $20,000 worth of damage - at the expense of ratepayers - when they graffiti-bombed the train at Meadowbank station," Sergeant Grant Harris said.

"We know there will be people out there who know, or can identify, those involved in this CCTV footage."

Several of the taggers are wearing video cameras on their heads and likely filmed their attack on the train.