President Donald Trump at the White House on Wednesday. REUTERS/Yuri Gripas

The White House's attempt to gather the personal data of US voters hit a legal roadblock Monday when a privacy advocacy group sued President Donald Trump's Advisory Commission on Election Integrity.

Last week, the commission asked election officials from all 50 states to submit troves of data about registered voters, including their names, addresses, party affiliations, and election-participation records.

But in a complaint filed in a Washington, DC, federal court, the advocacy group, the Electronic Privacy Information Center, called the commission's request "unnecessary and excessive" and said it would violate "the informational privacy rights of millions of Americans."

The center said the election commission must return any data it had received and complete a privacy-impact assessment before proceeding with the collection, Bloomberg reported.

The White House now has until Wednesday at 4 p.m. ET to respond to the group's request for a temporary halt on the data collection.

Several states refuse

More than 20 states have pushed back on the election commission's request to hand over voter data. On Monday alone, four states — Maryland, Delaware, Maine, and Louisiana — added their names to the list.

Several of the states have cited privacy concerns in their refusal to comply with the request, and some have charged the White House with political overreach.

Others have called the request an attempt to justify Trump's baseless claim that millions of illegal votes swung the popular vote toward his Democratic rival Hillary Clinton — a claim that election officials across the country have rejected.

"At best this commission was set up as a pretext to validate Donald Trump's alternative election facts, and at worst is a tool to commit large-scale voter suppression," Gov. Terry McAuliffe of Virginia said last week.