Union members at one of the largest publishing companies in the U.S, HarperCollins, went on strike Thursday. Workers walked out of the New York City office, saying they will not return until they have a new contract.

Union members have been without a contract since April and negotiations have reportedly stalled. Workers are aiming to receive higher wages, better family leave and stronger commitments to staff diversity.

HarperCollins employs around 4,000 people worldwide. The local 2110 chapter of the United Auto Workers Union (UAW) represents over 250 unionized HarperCollins employees across several departments – editorial, design, marketing, publicity, sales and legal.

In a memo sent to employees last week, HarperCollins said it had "implemented plans to ensure that operations continue uninterrupted during a potential strike."

Olga Brudastova, UAW chapter president, commented on HarperCollins' response in a statement.

"Late last week, the company communicated to us over email that they are not interested in scheduling more bargaining sessions and are rejecting our latest proposal," Brudastova said.

"We now get information that management is instructing non-union employees to avoid any mention of the strike and is planning to override our members' out-of-office messages that mention it."

Union members previously went on a 1-day strike earlier this summer and have been in negotiations with management since December. Signs from today's strike included, "Passion Doesn't Pay the Rent," and "Where the Wild Things Are Underpaid."

HarperCollins recently laid off a "small number" of workers, six of whom were union members. It follows a financial decline for the company, which reported an 11% drop in revenue last quarter and a 54% earnings loss.

Several authors who publish through HarperCollins have expressed solidarity with the workers on Twitter including Charish Reid, Micah Nemerever and Sarah Ruiz-Grossman.

The strike comes after the failed merger by fellow "Big Five" publishers as a federal judge struck down the merger of Penguin Random House and Simon & Schuster, stating that it could "substantially lessen competition."