The factory’s closure threatens to reduce the UK’s domestic capabilities and potentially force Leonardo to source the chips from elsewhere.

It would represent a blow to the UK at a time when the Government is seeking to build up the domestic industry for making semiconductors, a key technology underpinning everything from smartphones to complex computer systems and high-precision missiles.

A spokesman for Leonardo UK said: “Leonardo is aware of the current situation and is working with all of our stakeholders to deliver a resilient supply chain.”

On Monday, a Ministry of Defence spokesman said: “We continually monitor our supply chains, including in the semiconductor sector.”

One semiconductor industry source suggested a white knight investor may yet emerge to save the Coherent plant, adding: “There are potentially interested parties.”

The Telegraph first revealed in May that the site’s future was in doubt and undergoing a strategic review that could lead to the plant being sold.

In company accounts, Coherent said it had issued a last-time-buy notice to other customers.

It said the decision by Apple – which was not named in the accounts – to stop using the company as a supplier “places the ongoing viability of the business in doubt”.

The accounts added: “A strategic review of the business is currently being undertaken with potential new technologies and/or sale of the business as options under consideration.”

Losing a contract from Apple can often be disastrous for the company’s suppliers. The British semiconductor company Imagination Technologies lost half of its value and was eventually sold after Apple said it no longer planned to use the company’s graphics chip designs in 2017.

Other companies including Volex and Wolfson Microelectronics suffered share price plunges after losing contracts.

The Government announced a £1bn semiconductor strategy last year but critics say the money is not supporting the industry and pales in comparison to semiconductor subsidies in the US and Europe.

Coherent was asked for a comment on Monday but did not respond.