Ferry workers will refuse to sell or collect tickets on Saturday and Sunday between 6pm and 10pm on all Sydney services. For Manly ferries the action will take place between 6pm and 3am.

Fewer services will operate at the weekend due to overtime bans, while workers will refuse to help with charter services organised to deal with Vivid crowds. They will also refuse to operate the lights on Vivid ferry services between 7pm and 7.30pm.

The action follows a breakdown in pay negotiations between the Maritime Union of Australia (MUA), the Australian Institute of Marine and Power Engineers and the private operator, Harbour City Ferries.

The union has rejected a 9 per cent pay increase over four years and a proposal it says would see deckhands have their weekly pay cut by $500.

In a statement on Friday night, Ms Berejiklian said she was ''dismayed that the unions would choose to sabotage the Vivid festival and disrupt the journeys of so many people, including families. "I apologise in advance to customers who experience delays or disruption due to this disgraceful action.''

But MUA assistant branch secretary Paul Garrett said the union had talks with Harbour City Ferries 21 times over the past six months, including four this week.

''The union has remained committed to getting a fair outcome for ferry workers but we can't cop workers taking a $500-a-week pay cut, particularly after Tony Abbott's budget just three weeks ago,'' he said. Mr Garrett said the union was ''not on strike'' and that services would still run.

Harbour City Ferries chief executive Steffen Faurby said the company would endeavour to minimise the disruption to passengers.

''We are extremely disappointed by the actions of both the Maritime Union of Australia and the Australian Institute of Marine and Power Engineers, who have chosen to take industrial action during what will be one of the busiest weekends on the harbour."