Airbus has warned future investment in the UK could be under threat if Britain leaves the EU without a deal.
Senior Vice President Katherine Bennett said a no-deal Brexit would be “absolutely catastrophic” for the aerospace firm.
Meanwhile Theresa May plans to meet every European leader, begging them to let her renegotiate parts of her withdrawal agreement as the clock ticks down to March 29.
Airbus announced last week that it would be stopping production of its super jumbo A380 aircraft.
It said it had made the “painful” decision after struggling to sell the world’s largest passenger jet and after Emirates chose to slash its A380 order book by around a quarter.
While the decision was unrelated to Brexit, Ms Bennett said the current political landscape is a major worry for business.
Airbus chief executive Tom Enders has previously branded the Government’s handling of EU withdrawal a “disgrace” and said the company could pull out of the UK if Brexit undermines its ability to compete.
The firm employs some 14,000 people across two plants in the UK, and supports tens of thousands more British jobs in the supply chain.
Ms Bennett told the BBC “difficult decisions” will have to be made in the event of no deal.
She said: “What we’re concerned about is the prospect of a no-deal. There is no such thing as a manged no-deal, it is absolutely catastrophic for us and this is why we wanted to speak up.
“Our CEO has felt it important to speak up on behalf of our sector which is a really important contributor to the UK economy.”
She said they currently have a backlog of 9,000 aircraft to produce, providing plenty of work for UK employees for now, but added: “There will be decisions coming down the line in the next few years where my company will have to look seriously at investments.”
Airbus has spent tens of millions of euros on preparing for a no deal, including stockpiling parts, she said.
Ms Bennett said: “We are preparing for the worst and hoping for the best.”
Rejecting suggestions she is part of so-called Project Fear around Brexit, she said: “We think this is such a monumental thing that businesses have to speak up.”
Meanwhile Brexit Minister Chris Heaton-Harris has insisted the Government is not trying to run down the clock on Brexit.
He dismissed suggestions that the negotiations are a “complete waste of time”, and said there was a “huge amount of activity” between the UK and Brussels.
It comes after Theresa May issued a desperate plea to Conservative MPs to unite and deliver on Brexit, urging her party to “move beyond what divides us” and sacrifice “personal preferences” for the national interest.
The Prime Minister plans to speak to every European leader and European Commission chief Jean-Claude Juncker to seek changes to the withdrawal agreement.
Mr Heaton-Harris told Sky News: “The Government is not trying to run the clock down. The Government is trying to get a negotiated deal with our European partners.”
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