Industry sources said that a paperback book printing contract believed to be worth up to £7m-a-year was awarded to Clays two weeks ago, following a tender process. Clays already prints hardback books for the publisher.

Clays managing director Kate McFarlan confirmed that the company would be "extending its work" with Random House but said she could not give specific details.

Random House production director Stephen Esson had not returned calls at the time of writing, while a spokesman for CPI UK said it was the company’s policy not to comment on contractual matters.

It is known yet known what impact the contract loss will have on CPI; however, sources speculated that it could lead to job losses at the £121m-turnover group.

One source said: "If it is true that CPI has lost such a big contract, they will have to take appropriate measures to restructure the business to take account of it."