A 24-hour strike will begin from 4am on Saturday – the same day up to 500,000 people are expected to travel to the city, South Bank and major precincts along the Brisbane River for the fireworks extravaganza, which officially opens the Brisbane Festival.

The Maritime Union of Australia (MUA) and Australian Maritime Officers Union (AMOU) have periodically shut down ferries for hours at a time since July 30. But the move to shut down services on one of the biggest nights of the year for public transport, families and businesses is a major escalation.

Brisbane City Council was notified of the strike on Tuesday morning. But by 2pm, TransLink, the government-owned body responsible for public transport, was still advertising “extra” ferry services for Riverfire.

More than 27,000 passengers took ferry trips to and from Riverfire last year.

“This is clearly planned and co-ordinated to hurt the people of Brisbane,” Brisbane City Council’s Public Transport Chair Councillor Andrew Wines said. “Before this was announced, we had planned additional ferry services to help move passengers to and from the Riverfire event. Because of this action by the MUA, tens of thousands of passengers now face uncertainty.”

Brisbane Labor deputy leader Lucy Collier said the people of Brisbane were paying the price by being left stranded at Riverfire because Brisbane City Council had failed to sort weeks of strikes from “fed-up ferry workers”. “ … Instead of attacking workers, the people of Brisbane just want Brisbane’s Lord Mayor to step up and be a leader to get these workers a fair deal and get ferries and CityCats back on the river.”

RiverCity Ferries, a subsidiary of Kelsian and Sealink, operator of the Brisbane City Council ferries, says it has offered a 4.75 per cent first-year increase with more increases linked to the Fair Work Commission annual wage review. Mr Wines, at the council meeting on Tuesday, urged the ­ unions to call off the strike.

Maritime Union of Australia Queensland branch organiser Jaiden Simpson said ferry workers were standing up for basic standards. “These workers … carry responsibility for the safety of passengers and vessels, and they deserve to be treated with respect … RiverCity Ferries wants workers to accept a substandard deal while dressing up legal minimums as though they are generous new benefits.”

The MUA has said it is seeking paid parental leave and a 6 per cent increase in the first year, followed by either 4.75 per cent or the FWC increase, depending on which is higher.

The union said it was seeking a 12-hour break between shifts to address fatigue.

Mr Simpson said Brisbane City Council must take responsibility for the conditions being imposed on workers.

“Brisbane City Council cannot contract out its responsibility for decent work,” he said.

“If council wants a world-class ferry service, it needs to ensure the workers delivering that service get treated fairly.”