A state regulatory board has ruled that one of the men charged with setting tax values on Fulton County properties isn’t fit to appraise residential real estate.

The Georgia Real Estate Appraisers Board voted Monday to revoke Donald Johnson’s professional appraiser’s license, creating fresh ammunition for critics who contend that Fulton systematically overtaxes homeowners through overstated values.

Now a battle may be brewing over Johnson’s seat on the Fulton County Board of Assessors, although county commissioners lack the authority to recall appointees to the board.

Johnson is one of five board members who oversee the setting of fair market values on homes, businesses and land lots throughout the county, which determines how much taxpayers get billed.

R.J. Morris, a frequent foe of the assessor’s office, said that given the tax office’s checkered record over the past few years, Johnson should resign.

“The Board of Assessors is judging over 300,000 parcels,” Morris said. “They’re judging billions of dollars in values. They have to be trusted.”

That trust may have been tested in recent years by a string of incidents and controversies.

In August an estimated 6,500 to 7,000 property owners received overvalued tax bills because one department, the tax assessor’s office, did not key tax appeals into a computer system before another department, the tax commissioner’s office, generated 2012 bills. Chief Appraiser David Fitzgibbon attributed the delay partly to a flooded workspace during heavy rains in July, and Tax Commissioner Arthur Ferdinand said sending corrected bills would cost about $2,000.

Last year, the county sent overvalued estimates on tax bills to about 136,000 Atlanta property owners, which was attributed to a computer glitch and careless staff. The county wound up remailing 230,000 assessment notices, costing an estimated $140,000. Then research by Morris revealed Fulton had appraised dozens of properties higher than what they sold for in 2010, contrary to a new state law.

The board’s vote Monday rejected a recommendation last month from Administrative Law Judge Ana Kennedy that Johnson receive a six-month suspension. She said then that there was insufficient evidence that Johnson took part in fraud.

Commissioner Bill Edwards, who nominated Johnson, said he will ask him to step down this week. Johnson, however, is refusing, saying his position as an assessor has nothing to do with his private career as an appraiser.

“How can what I do affect that whole board?” said Johnson, a self-employed appraiser based in south Fulton. “I’m just one of five people.”

Johnson has 30 days to appeal the revocation to Fulton County Superior Court. He said Monday that he and his attorney haven’t decided whether to pursue that.

Meanwhile, by state law, the County Commission can’t force out a member of the Board of Assessors over a private business matter. Johnson doesn’t need a license to serve, and he’s one of just three members who have been licensed appraisers.

Edwards says that in a private meeting in April, Johnson promised that if the state found him in any way at fault, he would resign. Johnson maintains he only said he would quit if the state proved he took part in mortgage fraud and intentionally inflated appraisals.

Edwards said he’s now consulting with the county attorney about his options. County commissioners nominate members to the Board of Assessors, with the full commission voting to formally appoint them. Their terms range from three to five years. Johnson’s four-year term ends in June 2014.

“I’ve been very patient, and I’ve not been quick to judge,” Edwards said. “Obviously, with the revocation of the license, he’s been found guilty.”

Supporting Johnson, though, is Board of Assessors Chairman Bill Huff, who says Johnson’s expertise on south Atlanta and south Fulton properties is invaluable.

“I think the whole thing was bogus,” Huff said of the state’s case against Johnson, “and the charges were unfounded.”

Fulton faced a similar situation last year, when the County Commission asked north Fulton appointee Rick Kenny to resign after learning that the state board deemed him “negligent” in overvaluing a duplex in 2005. Rather than face a hearing and risk having his appraiser’s license pulled, Kenny agreed to pay $5,000 in administrative and legal costs and take six hours of classes on mortgage fraud. He refused to resign and remains on the board.

The state appraisers board slapped Johnson for overvaluing three quadruplexes on Hollywood Road and a townhouse on Moreland Avenue between 2005 and 2007.

Appraisals must cite sale prices of nearby, similar properties, and Johnson is accused of using selective sales — many of them inflated — to boost values. In one case, the state contends, he set a quadruplex’s value at $345,000, ignoring nearby sales of $162,500 and using data provided by the mortgage company and a closing attorney.

Johnson has said that before the crash, real estate values were still going up, and the neighborhoods where he did the four appraisals seemed to be up and coming. He has also said that many of the nearby sales that the state says he should have used for comparables weren’t available to him because, at the time, Fulton had a backlog in putting sales data on the Web.

Robert Tindall bought two of the buildings on Hollywood Road based on Johnson’s opinion that their value was in the $350,000 range.

Like other investors who bought into the complex, Tindall wound up in foreclosure.

“It ruined me financially. It ruined me personally,” Tindall said. “The most important thing is his license, but I can’t imagine him working in anything that involves land values.”