One architect and planner who has been involved in tracking projects in the streets around Flagstaff station has estimated about 30,000 new residents will live in the area when all the apartments being built are finished.

Labor and the Coalition both promised to open Flagstaff during last year's election campaign.

Public Transport Minister Jacinta Allan said on Monday: "Opening Flagstaff station on weekends will unlock the north-west corner of the city, making it easier for people to get to Queen Victoria Market or Flagstaff Gardens, and for locals to get to work and get home."

Flagstaff's opening will coincide with the launch of 24-hour public transport in Melbourne. From January 1, trains will run hourly from Flinders Street Station on all metropolitan lines, and trams will operate every 30 minutes on six routes – 19, 67, 75, 86, 96 and 109.

Night buses will depart from the CBD about every half-hour, and from suburban stations including Elsternwick, Ringwood, Dandenong and Frankston every hour.