LONDON — The UK tech company Imagination Technologies on Monday announced that Apple, its biggest customer, would no longer be using its tech.

Imagination said in a statement: "Apple is of a view that it will no longer use the Group's intellectual property in its new products in 15 months to two years time, and as such will not be eligible for royalty payments under the current license and royalty agreement."

The news sent Imagination's share price collapsing. Its stock opened down by over 60% and fell even further as trading got underway in earnest in London. Shares were down over 70% just after 8:45 a.m. BST (3:45 a.m. ET): A share-price collapse of this magnitude is hugely unusual for a listed company of Imagination's size. Monday morning's collapse has wiped over £500 million ($625 million) off Imagination Technologies' market value.

Imagination has long supplied graphics-processing chips to Apple that are used in its iPhones, iPads, and Watches. Apple is also Imagination Technologies' third-largest shareholder.

Imagination, however, said on Monday: "Apple has asserted that it has been working on a separate, independent graphics design in order to control its products and will be reducing its future reliance on Imagination's technology."

Apple considered buying Imagination last year but ultimately decided against it. Since then, Business Insider has reported on how Apple has hired key talent away from Imagination. The most senior hire was Imagination's former COO John Metcalfe, a 20-year veteran of the UK company.

Imagination on Monday said it was prepared to fight Apple, suggesting that the tech giant may infringe upon Imaginations' patents by developing in-house solutions.

Imagination said:

"Apple has not presented any evidence to substantiate its assertion that it will no longer require Imagination's technology, without violating Imagination's patents, intellectual property and confidential information. This evidence has been requested by Imagination but Apple has declined to provide it.

"Further, Imagination believes that it would be extremely challenging to design a brand new GPU architecture from basics without infringing its intellectual property rights, accordingly Imagination does not accept Apple's assertions.

"Apple's notification has led Imagination to discuss with Apple potential alternative commercial arrangements for the current license and royalty agreement.

"Imagination has reserved all its rights in respect of Apple's unauthorised use of Imagination's confidential information and Imagination's intellectual property rights."

Imagination's stock soared in the first half of the decade as it rode the smartphone boom. The company has fallen on difficult times in recent years, however, because of a slowdown in the market. Last year it posted its biggest loss in history, £61.5 million.

Imagination announced a huge overhaul of the business last year that included £12.5 million of cost-cutting and more than 200 jobs being axed. Long-standing CEO Sir Hossein Yassaie also left the business.