GMB Scotland and Unite Scotland said that 35 of the remaining 43 core staff were handed statutory redundancy notices on Friday.
It follows the announcement in mid-April that Canadian company JV Driver, through its subsidiary DF Barnes, had acquired BiFab following extensive negotiations with the Scottish Government.
The trade unions vowed their “battle for BiFab” will continue as they campaign for the future of the yards in Burntisland and Methil in Fife and Arnish on Lewis.
Trade union secretaries Gary Smith, of the GMB, and Unite’s Pat Rafferty said in a joint statement: “The scale and speed of these redundancies was not expected. It means that some workers will be out of a job as early as two weeks’ time and most will be gone in three months.
“But the trade unions will not be found wanting and our battle for BiFab continues. We knew the road ahead would be hard and the need for new contracts is obvious but clearly a major problem has emerged in terms of the future prospects for fresh work over the last fortnight.
“As a matter of urgency, we need to understand what those problems are and whether they can be overcome in the short term. We are working now with the employer and the Scottish Government to achieve this objective.”
Figures released by the Scottish Government, which are believed to take in the full employment picture at the firm beyond the core staff on the shop floor, show that BiFab had 132 employees and 128 contractors a week ago.
Of the permanent employees, 56 were already on notice and an additional 40 received notices on Friday, meaning that there will be 36 permanent employees working alongside contractors once the notices take effect.
Scottish Labour’s economy spokeswoman Jackie Baillie MSP described the latest move as “deeply disappointing” and said: “Given the Scottish Government now has a stake in BiFab, it is essential that they intervene to stop any job losses and secure further work for the three BiFab sites.”
A Scottish Government spokesman said: “The acquisition of BiFab by DF Barnes represents a significant step forward in our efforts to restore BiFab to its place at the centre of Scotland’s marine energy industry. But there is a lot of hard work ahead.
“As ministers made clear when new ownership was secured, while the current contract comes to an end and efforts go into winning new work, there will continue to be difficult times for the three yards.
“But the commitment of DF Barnes gives BiFab the best chance of winning future contracts and securing new work.
“Nonetheless, this announcement will be hugely concerning for the workers affected and their families - we are in regular contact with the unions and we stand ready to provide support through our Partnership Action for Continuing Employment (PACE) initiative.
“By providing skills development and employability support, PACE aims to minimise the time individuals affected by redundancy are out of work.”