The Trump administration denied on Wednesday that it had returned Michael D. Cohen to prison in retaliation for his decision to publish a jailhouse tell-all book about his former boss, the president.

The government said in newly filed court papers that the decision to send Mr. Cohen, President Trump’s former fixer and lawyer, back to prison earlier this month after he had been released on furlough was made by a federal Bureau of Prisons employee. That employee had no idea that Mr. Cohen was writing a memoir, the papers said.

Instead, Mr. Cohen endangered his own freedom by becoming “combative” when refusing to sign an agreement outlining the terms of his release, the government said. The agreement was “not devised by anyone at B.O.P. or in the executive branch — let alone a high-level official with any motive to prevent the release of” Mr. Cohen’s book, the papers said.

The new filing came in response to a lawsuit Mr. Cohen filed on Monday against Attorney General William P. Barr and the director of the Bureau of Prisons, demanding that he be released and allowed to serve the remainder of his sentence in home confinement.

In the suit, Mr. Cohen asserted that the government had violated his First Amendment rights by returning him to custody in what he said was retaliation for his book project, making it impossible for him to complete the manuscript.

Judge Alvin K. Hellerstein of Federal District Court in Manhattan has set a hearing on the matter for Thursday.

Mr. Cohen’s lawsuit has drawn support from the American Civil Liberties Union, which joined private lawyers in helping to represent him, as well as from legal scholars.

This week, a group of constitutional law professors filed a brief in the case, saying they were “deeply concerned about the blatant disregard for First Amendment rights and values displayed in the treatment of Mr. Cohen.”

Mr. Cohen, 53, pleaded guilty in 2018 to campaign finance violations and other crimes, stemming from a scheme to pay hush money to two women who said they had had affairs with Mr. Trump before he was president. Mr. Trump has denied the allegations.

Mr. Cohen had been serving a three-year sentence at a minimum-security prison camp in Otisville N.Y., about 75 miles northwest of New York City.

He said in his lawsuit that he had been writing his book “in plain sight” in a prison library at Otisville and had discussed it with other inmates, prison officials and staff members.

The suit said the book would include Mr. Cohen’s “firsthand experiences with Mr. Trump” and “graphic details about the president’s behavior behind closed doors.”

“The narrative describes pointedly certain anti-Semitic remarks against prominent Jewish people and virulently racist remarks against such Black leaders as President Barack Obama and Nelson Mandela,” according to the suit.

The book was tentatively titled “Disloyal: The True Story of Michael Cohen, Former Personal Attorney to President Donald J. Trump,” the suit said.

Then, in May, Mr. Cohen, whose lawyers have said he has severe hypertension and respiratory issues, was released on furlough as a part of an effort by the Bureau of Prisons to curb the spread of coronavirus in its facilities. He continued to work on his project at home and also publicized it, announcing plans to publish the book in late September, before the election.

On July 9, Mr. Cohen was abruptly sent back to prison after he balked at signing an agreement that would have allowed him to remain home if he agreed not to publish the book for the duration of his sentence. His projected release date from prison is November 2021.

“The timeline here clearly indicates retaliation,” the lawsuit said.

But in its response, the government described the behavior of Mr. Cohen while meeting with probation officers to consider the agreement as “defiant” and “unacceptable.”

The government asserts that Mr. Cohen told the officers that he was going to write a book “no matter what happens.” He also objected to a provision that restricted his employment, asking whether he could appear “as a political correspondent on television or the radio,” the government filing said.

It added that Mr. Cohen also told one officer to “say hello to ‘Mr. Barr.’”

Since his return to prison, Mr. Cohen has been held in solitary confinement virtually around the clock, making it impossible for him to complete his book, according to the suit.

The government responded in its filing that Mr. Cohen was isolated after being returned to Otisville under a policy that says new inmates are quarantined for about two weeks before being allowed to enter the prison’s general population.

He is to be tested for the coronavirus on Friday, the government said, adding, “He is free to work on his book while incarcerated.”