The pledge would also see a new zero-emissions bus depot in Canberra's north, and the upgrading of the Woden Depot to cater for electric buses. It would cost $114 million over the next four years to implement the plan. The government says it is on track to transition every public bus to zero emissions by at least 2040.

Transport Minister Chris Steel said under a Labor government, no new diesel buses would be purchased from 2025.

He said if re-elected, the government would go out to market at the end of the year to find an electric bus provider. The ACT undertook a previous trial of electric buses but they were plagued with reliability issues, and two buses missed more than one-third of their services.

More recently, the government has leased a more advanced bus from Chinese company Yutong, and Mr Steel says it has been far more reliable.

"We've learnt a lot from that in terms of the need to have a partner that can work with us," he said. "And making sure we've got a range of spare parts."

Each vehicle costs about $750,000, but he said new developments were constantly pushing the price down.

"There are a range of different companies who have newly emerged so we want to test the market," Mr Steel said. The plan would help reduce Transport Canberra emissions by about 17 per cent. Mr Steel said the move would require extra mechanics skilled with electric vehicles. But he said diesel mechanics currently employed by Transport Canberra would be upskilled to work on the new buses.

An additional 64 bus drivers would be recruited from 2024 to support the running of the expanded fleet. The ACT's public transport network currently has about 450 buses, a number which is expected to grow to 590 by 2031.