By David Ingram

WASHINGTON, Feb 8 (Reuters) - Publishing house Macmillan on Friday became the fifth and final U.S. book publisher to sign a settlement with the government in a sweeping antitrust case that accused them of conspiring to raise e-book prices.

Macmillan and the Justice Department filed the proposed settlement, which requires a judge's approval, in U.S. District Court in Manhattan.

A small firm that is also known as Holtzbrinck Publishers LLC, Macmillan was the lone holdout among five publishers that the government sued in April 2012. Three publishers settled immediately and the fourth, Pearson Plc's Penguin Group, settled in December.

The Justice Department will continue to litigate conspiracy allegations against Apple Inc, the department said in a statement. It accuses Apple of conspiring with the publishers to raise prices and fight the dominance of Amazon.com Inc.

Apple rejects the allegations, saying it did not collude but signed agreements with publishers individually. Apple has also said in court papers that the government's suit "sides with monopoly, rather than competition," by shoring up Amazon's early advantage in electronic books.

A civil trial for Apple is scheduled to begin in June.

Bookseller Barnes & Noble Inc has sided with Apple, telling the federal court that it, too, is concerned about a monopoly by Amazon.

Macmillan Chief Executive John Sargent was a defiant critic of the suit, saying when it was filed that his company did not collude and that settlement terms required by the Justice Department "would have a very negative and long term impact on those who sell books for a living."

Sargent did not immediately return a message left at his office on Friday. Macmillan is a unit of Verlagsgruppe Georg von Holtzbrinck GmbH, based in Germany.

Under the proposed settlement agreement, Macmillan must lift restrictions on discounting by e-book retailers and must report to the Justice Department its communication with other publishers.

Justice Department lawyers "expect the prices of Macmillan's e-books will also decline," as happened after settlements with the other publishers, Jamillia Ferris, chief of staff of the department's Antitrust Division, said in the news release.

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