Aerospace firm Airbus, which makes wings in Flintshire, has warned it could pull out of the UK with the loss of thousands of jobs if there's a "no-deal" Brexit.
The firm, which employs over five thousand at Broughton, says it would "reconsider its investments in the UK, and its long-term footprint in the country" if Britain crashed out of the single market and customs union without a transition agreement.
Publishing a Brexit 'risk assessment' on its website, the firm also called on the Government to extend the planned transition period due to run until December 2020 if a deal is agreed, saying it was too short for the business to reorganise its supply chain.
If there was no extension it would "carefully monitor any new investments in the UK and refrain from extending the UK suppliers/partners base", it said.
In any scenario, Brexit has severe negative consequences for the UK aerospace industry and Airbus in particular. Therefore, immediate mitigation measures would need to be accelerated.
The Welsh Government said the announcement is worrying.
The announcement from Airbus is extremely worrying. We have repeatedly warned that the UK cannot take the huge economic risk of cutting ourselves adrift from the Single Market and Customs Union. Particularly in the case of manufacturing sectors, which in Wales are so important in providing high-paid, high-skilled jobs. We have again today called on the UK Government in its forthcoming White Paper to commit to staying inside the Single Market and Customs Union.
Meanwhile, Conservative MP Stephen Crabb described the news as a "wake-up call".
The former Secretary of State for Wales said: "The enormous Airbus factory in North Wales is one of the jewels in the crown of UK manufacturing.
This is a wake-up call. A pragmatic, sensible Brexit that protects trade & jobs is vital."