It could be months before all of the seats are reinstalled on Wellington's buses.

Seats were taken out of some buses earlier this year to help with capacity problems.

The decision faced backlash from commuters and prompted the regional council to commit to putting them back.

But not all the seats are back yet and City councillor Sarah Free is concerned about the issue.

"I was told yesterday they've started the process but it won't be completed until next March which is a worry."

Free says it seems like a lot of time and she is not sure why it's taking them so long.

"I want to know what is happening when there are not enough straps for people to hold onto to ensure people's safety."

A Metlink spokesperson says the reinstatement of seats takes the bus out of action for a number of days.

The process may take months and will likely not be completed until March next year. The buses also need to be re-certified which will add to the timeframe.