As Loudoun County assessor, Todd Kaufman headed a team that determined the real estate value of every property in the wealthiest county in America. He received glowing job evaluations and numerous awards.

Then, on April 18, he was escorted from the County Government Center without warning, and on June 5, he was fired by the County Board of Supervisors.

Now, Kaufman, 51, contends in a newly filed lawsuit that an anonymous letter sent by a disgruntled employee in March sparked an investigation, that the employee’s allegations were false and that Kaufman was not allowed to meet with the Board of Supervisors before he was fired.

Kaufman took over as the county assessor in 2005 and was an “at-will” employee of the Board of Supervisors. When board members decided to fire him, they were required, under the terms of his contract, to pay him nine months’ salary plus accumulated leave, which totaled $148,787, Loudoun officials said last month.

Kaufman’s lawsuit, filed Monday in Loudoun County Circuit Court, alleges defamation, conspiracy and tortious interference against three county officials and an outside investigator. He is seeking economic damages, including the loss of wages and future income — his annual salary was $147,015 — and punitive damages. He is not seeking reinstatement.

Kaufman alleges that John D. Nelson, the supervising appraiser in charge of commercial and industrial appraisals, who reported to Kaufman, sent an unsigned, single-spaced five-page letter to County Administrator Tim Hemstreet on March 27. The letter alleges various offensive statements or physically threatening actions by Kaufman. Nelson was quickly identified as the letter’s author, the suit states.

Kaufman claims that Hemstreet and Loudoun County Attorney John R. Roberts conspired to place only negative or untrue information about him before the Board of Supervisors, leading to his sudden ouster, and that Hemstreet and Roberts advised the board not to hear Kaufman’s side.

Nelson, Hemstreet and Roberts are named as defendants in Kaufman’s lawsuit. They did not respond to phone calls and e-mails seeking comment Thursday.

After Nelson’s letter was received, the county hired an independent mediator, James R. Cross of Manassas, to investigate. Cross interviewed Kaufman and 18 other current or former county employees, and he prepared a seven-page report, submitted May 15, that ignored some of Nelson’s allegations, deemed a claim of sexual harassment “not sustained” and concluded that Kaufman had not created a hostile work environment.

But the report also found that Kaufman made inappropriate comments and managed his employees “in a manner that was threatening, intimidating and bullying.” Cross concluded that Kaufman had violated a county policy prohibiting “minor use of offensive or discourteous language” and had possibly violated a prohibition against the “use of abusive or threatening language toward the public or other employees.”

Cross, also named as a defendant in Kaufman’s suit, would not comment Thursday.

Neither Loudoun County nor any member of the Board of Supervisors is named as a defendant, and no county official has ever publicly explained why Kaufman was fired. Board Chairman Scott K. York (R) said he could not discuss the suit. County spokeswoman Anna Nissinen said she had not seen the suit and could not comment.

Before Cross issued his report, Kaufman wrote a detailed letter to the Loudoun supervisors — included as an exhibit in the lawsuit — defending his work and pointing out that no one had raised a complaint with him before Nelson’s letter. He said that Nelson had been a troubled employee, that he had cobbled together a list of unrelated complaints over five years and that he was retaliating against Kaufman because requests for extended vacation had been denied and because he had been counseled to improve his work.

After Cross’s report went to the board, Kaufman sent another letter to the supervisors requesting a meeting, according to an exhibit submitted with the lawsuit. The suit contends that Roberts and Hemstreet advised board members not to meet with Kaufman and that they didn’t. He was fired and paid the $148,787 in severance.

Kaufman said Thursday that his suspension and firing took him totally by surprise. “All the feedback I got was that I was doing a good job,” he said. “We have had no contact with the Board of Supervisors. I have no idea what was discussed, what their mind-set was, I was just left in the dark.”

He said that if the board had philosophical differences with him and decided to hire someone else, “I have no problem with that. I have a problem with how they handled it.”

Kaufman’s attorney, Peter C. Cohen, said Kaufman “did what the board hired him to do — to make the office the professional office that it is today, and he feels strongly about the way that the county and officials handled the matter.”

The lawsuit goes through each of Nelson’s allegations, such as that “Kaufman went one-by-one to all members of staff that was present asking ‘what their religious beliefs were’ ” and states that they are false.

Cross’s report found that Kaufman had made sarcastic remarks about Christians and Greeks, had belittled older employees as “menopausal” and unfit for new training and had called the county board “the Board of Stupid-visors.” Kaufman’s suit repeatedly denies those claims.

Cross found that no one was offended or felt harassed by Kaufman’s sexually related comments. But Cross reported that some employees felt physically threatened, and he cited incidents in which Kaufman allegedly pointed his finger at one person and shoved another.

Kaufman’s response letter said both incidents were misrepresented.