Houston Mayor Sylvester Turner on Monday urged Harris County's voter registrar to reject calls from state leaders to question the citizenship status of thousands of registered voters, calling the effort a "manifestly slapdash process."

In a letter to Tax Assessor-Collector Ann Harris Bennett, Turner wrote that officials had used inaccurate and arbitrary data when they advised Texas counties to mail letters requesting proof of citizenship from registered voters who had indicated they were not citizens when they obtained their driver licenses.

"There is nothing suspicious about an individual being registered to vote even though he or she was once listed as a non-citizen – as far back as 1996," Turner wrote. "It stands to reason that the vast majority of these people are simply among the hundreds of thousands who have become naturalized U.S. citizens."

RELATED: Harris County pushes back against state's call for voter purge

Turner's letter takes aim at Secretary of State David Whitley and Attorney General Ken Paxton, who have been named in a growing number of lawsuits over Whitley's Jan. 25 advisory that claimed Texas' voter rolls may contain nearly 100,000 non-citizens.

Without proof that people named on the list were not citizens, Harris County hesitated to query voters on their citizenship status, and quickly found that Whitley's list contained 18,000 voters who were erroneously flagged, making up about 60 percent of the original count here.

The secretary of state's office pushed back on Turner's claim that their citizenship data – which was gathered from Department of Public Safety driver license and ID card information – goes back to 1996.

Actually, spokesperson Sam Taylor said, it is the voting history that dates back to 1996. The DPS information is current, Taylor said.

Already, a handful of lawsuits are seeking injunctions that would block counties from taking action on the advisory.

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Citing Houston's diverse population and large number of immigrants and naturalized citizens, Turner cast the state's attempted voter purge as an effort to undermine the city's identity.

"I urge you to resist carrying out this short-sighted policy that degrades the very people who have worked so hard to meet our citizenship requirements and play by the rules," Turner wrote to Bennett.

Bennett's office did not immediately respond to a request for comment.

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