Apple lost a high-profile court battle yesterday, when a US federal judge ruled that it violated antitrust law by playing a leading role in a conspiracy with publishers to increase the price of ebooks.

Denise Cote, a federal judge in New York, cited “admissions” by the late Steve Jobs, as well as emails and telephone calls between Apple, Amazon and publishing executives as proof that Apple acted as a ringleader in a price-fixing conspiracy when it launched its digital books business.

“Without Apple’s orchestration of this conspiracy, it would not have succeeded as it did,” said Judge Cote, who presided over the three-week non-jury trial. “Apple and the publisher defendants shared one overarching interest – that there be no price competition at the retail level.”