Bombardier is Northern Ireland's largest manufacturing employer

Fears are growing that Bombardier Shorts will press ahead with job cuts after the negotiations broke down on Tuesday.

More than 1,000 jobs are under threat at the company after 60% of workers voted in May to reject a proposed four-year agreement over pay.

Negotiations were to continue on Wednesday, but union leaders said they had failed to resolve two issues that were in dispute at preliminary talks over the weekend.

They accused the company of undermining the talks through their "inflexible position".

A Shorts spokesman said they were "disappointed" the unions had chosen to walk out and said the company was fully committed to finding a solution.

They weren't prepared to take these preconditions off the table so we had no option but to walk out Peter Williamson Union official

The company has already announced 580 redundancies in response to what it called "very challenging market conditions".

Tuesday's walkout marked a change in relations between the parties, as both Bombardier Aerospace and a union source described talks held last Wednesday as "constructive".

Peter Williamson from the manufacturing, science and finance union Amicus, who is leading the union's delegation in the talks, said on Tuesday that they were forced to walk out because management refused to withdraw two preconditions.

Management stood firm on the uptake of apprenticeships and the payment of holiday entitlements.

"Clearly the company were not prepared to enter into constructive negotiations," he said.

"They weren't prepared to take these preconditions off the table so we had no option but to walk out.

Our priority has always been, and still remains, our employees, and the long-term future of the company Bombardier spokeswoman

"All management need to do is to give us dates when the apprentice issue will be dealt with and when the outstanding money will be paid and we will re-enter talks.

A spokeswoman for Bombardier said the issues of apprentice intake and holiday entitlement were only tabled by the union delegation at preliminary talks last week.

"We have consistently and repeatedly expressed our willingness and desire to reach an agreement, and totally refute any claims calling that commitment into question," she said

"Our priority has always been, and still remains, our employees, and the long-term future of the company."

Bombardier in Canada has already made it clear that it needs to reduce the workforce in Northern Ireland in order to improve competitiveness.

It said it was essential that the company was "in the best position possible to retain contracts with its customers who are demanding very competitive, long-term price commitments".

The aerospace industry has been badly affected in recent years by events including 11 September, the consequent fear of terrorism, the downturn in the global economy, competition from low-cost carriers and the recent Sars outbreak.

Many airlines are in financial difficulties and have cancelled some aircraft orders and putting others on hold.