The GMB union is urging BAE, operator of the Govan and Scotstoun dockyards, to be cautious in its approach to merger plans and has called on the Government not to stand aside during the attempt to create a European giant to compete with US rivals.
Prospect, who represent professional and engineering staff, also expressed concern yesterday. Incoming general secretary Mike Clancy said all defence contractors had been under immense pressure because of spending cuts. He said: "Whether the news of this merger brings reassurance or not for the workers depends on whether the new company will go for consolidation or growth.
"We are seeking early talks about the future strategic positioning of the business. We are puzzled as to why BAE has decided to merge with EADS, even though it cut formal ownership ties with Airbus only a few years ago."
That break-up ended in acrimony in 2006 as news of delays in the projects caused a fall in share price just as BAE was trying to divest its share.
Mr Clancy added: "BAE Sys-tems is a prime contractor of the Ministry of Defence, and this move clearly reflects fears about future profitability of those arrangements as defence markets shrink."
The firm, which has more than 3000 employees in Scotland, mainly on the Clyde, is adding nothing to its Stock Exchange statement about merger talks on Wednesday but most defence analysts think the shipbuilding sector would be protected from any rationalisation.
Jim Moohan, senior Scottish organiser of GMB and chairman of the shipbuilding and engineering unions, said: "As we now have stability with job protection, capital investment and recruitment of hundreds of apprentices, it is important we do not jeopardise the time and effort put into achieving this.
"We can ill afford to make mistakes from which the UK employment sector could very well face long-term consequences. The trade unions would suggest caution is the key and would ask BAE Systems to ensure that, from the very outset, they engage totally with the trade unions who they have a very good relationship with and also that the UK Government do not stand aside from a merger."
BAE and EADS, the French-German-Spanish conglomerate, fell out over the civilian Airbus project, but have continued to collaborate on the Eurofighter Typhoon jet and both have a share in the MBDA missile firm.
If they overcome the regulatory hurdles and merge, BAE shareholders will own 40% of the combined business and EADS shareholders 60%. They would have combined sales of £60bn and employ 220,000 people worldwide.