Thousands of construction workers will stage another industry walkout next week as part of a new “line in the sand” campaign that building unions say will run the entire five years of the CFMEU’s administration, and could involve three-day strikes.

About 700 delegates from building unions, including the Electrical Trades Union and the CFMEU, gathered on Thursday at Melbourne’s Moonee Valley Racecourse where they voted to rally on Wednesday against employers allegedly trying to walk away from agreements, and threatened a 72-hour strike if any pay deals were held up.