Labor says if it wins government in November it will stop Metro's policy of skipping train stations and locking in passengers in order to make up lost time.

It follows a warning from Victoria's Public Transport Ombudsman that commuters must be warned before a train switches to express and starts skipping stations.

Metro on Monday conceded that some peak-hour services are switching to express and that this was "the wrong decision".

Ombudsman Janine Young said customers needed timely information to make informed decisions on whether to board a train or wait for the next one.

"If a train is going to express, an announcement will allow people to not catch that service and wait for the next one," she said.