MILWAUKEE — Milwaukee Mayor Tom Barrett raised concerns Wednesday that as many as 32,000 voters in the city were mistakenly deactivated because of erroneous information but election officials say the number is much smaller.

Barrett sent a letter to Republican Gov. Scott Walker Wednesday explaining that inaccurate information from the state DMV and postal service led to the errors in the Electronic Registration Information Center. More than 20 states use the system and it’s designed to maintain up-to-date voter rolls.

Voting access is a contentious issue in Wisconsin, where Democrats have long criticized Republicans for passing a law requiring photo identification at the polls. Republicans argue the law is designed to prevent fraud, but Democrats say it’s a GOP effort to depress turnout among the elderly and minority voters.

Voters are deactivated if they fail to vote in four years or move and don’t update or verify their address through a postcard mailed to them.

“We think that a substantial number of them did actually move,” said Reid Magney, a spokesman for the Wisconsin Elections Commission. He said that’s “based on postcards coming back as undeliverable.”

Barrett said the problem came to the city’s attention last month during primary elections when about 100 people needed to re-register because they had been deactivated, even though they lived at the same address or had voted within the last four years.

Magney disputed the city’s assertion that 100 voters needed to re-register. He said his office has only confirmed a dozen such cases and he believes only “a relatively small percentage” of the 32,000 deactivations were in error.

In the letter to Walker, Barrett urges the governor to work with the state’s election commission to reactivate everyone who was wrongfully deactivated.

“Let’s iron out the problem so that people are not coming to the polls and denied the right to vote,” Barrett said during a news conference. “For some people it’s easy to re-register. Others it may not be so easy and we don’t want to discourage people from voting.”

The number of registered voters has quickly decreased in Milwaukee, going from about 330,000 before the 2016 presidential election to about 248,000 currently, said Neil Albrecht, the executive director of the Milwaukee Election Commission.

“That number is about the lowest our voter registration records have been in 50 years,” he said.

Most of the decrease is due to updates to voter rolls to remove inactive voters or those who moved elsewhere.