WASHINGTON >> President Donald Trump signed an executive order today launching a commission to review alleged voter fraud and voter suppression, building upon his unsubstantiated claims that millions of people voted illegally in the 2016 election.

The White House said the president’s “Advisory Commission on Election Integrity” would examine allegations of improper voting and fraudulent voter registration in states and across the nation. Vice President Mike Pence will chair the panel and Kansas Secretary of State Kris Kobach will be vice chair of the commission, which will report back to Trump by 2018.

Trump has alleged, without evidence, that 3 million to 5 million people voted illegally in his 2016 election against Democrat Hillary Clinton. He has vowed since the start of his administration to investigate voter fraud, a process that has been delayed for months.

Democrats and voting rights groups called the panel a sham, arguing there are few, if any, credible allegations of significant voter fraud. They warned that the panel would be used to lay the groundwork for stricter voting requirements that could make it more difficult for poor and minority voters to access the ballot box.

“The sole purpose of this commission is to propagate a myth and to give encouragement to Republican governors and state legislators to increase voter suppression,” said Vermont Sen. Bernie Sanders, who challenged Clinton for the Democratic presidential nomination.

Senate Democratic Leader Chuck Schumer of New York said it was a “clear front for constricting the access to vote to poor Americans, older Americans, and — above all — African-Americans and Latinos.”

White House spokeswoman Sarah Huckabee Sanders said the commission would be bipartisan and composed of about a dozen members, including current and former state election officials and experts.

“The president is committed to the thorough review of registration and voting issues in federal elections and that’s exactly what this commission is tasked with doing,” Sanders said.

The panel will aim to ensure confidence in the integrity of federal elections while looking at vulnerabilities in the system and the possibility of improper voting and fraudulent voter registration and voting, officials said.

The commission will include two Republicans, former Ohio Secretary of State Ken Blackwell and Indiana Secretary of State Connie Lawson, and two Democrats, New Hampshire Secretary of State Bill Gardner and Maine Secretary of State Matthew Dunlap.

Christy McCormick, a former Justice Department attorney and a member of the U.S. Election Assistance Commission, will also be on the panel, and others will be named soon.

Trump repeatedly alleged that the election system was “rigged” during his campaign and later argued that massive, widespread fraud kept him from winning the popular vote. Trump won the presidency with an Electoral College victory even though Clinton received nearly 3 million more votes.

Voting experts and many lawmakers, including House Oversight Committee Chairman Jason Chaffetz, have said they haven’t seen anything to suggest that millions of people voted illegally. The Utah Republican said his committee won’t be investigating voter fraud.

But in a lunch meeting with senators in February, Trump said he and former Republican Sen. Kelly Ayotte would have won in New Hampshire if not for voters bused in from out of state. New Hampshire officials have said there was no evidence of major voter fraud in the state.

Michael Waldman, president of the New York-based Brennan Center for Justice, said the commission was formed to “find proof of the president’s absurd claim” about millions of people voting illegally. He noted that it came in the aftermath of Trump’s firing of FBI Director James Comey on Tuesday.

“He fired the person investigating a real threat to election integrity, and set up a probe of an imaginary threat,” Waldman said.

Trump had previously identified Pence as the person to oversee the commission. Kobach advised Trump’s transition team and has been a leading GOP proponent of tighter voting regulations.

The secretary of state championed Kansas’ proof-of-citizenship requirement as an anti-fraud measure that keeps noncitizens from voting, including immigrants living in the U.S. illegally.

Critics contend it suppresses voter turnout, particularly among young and minority voters, and that there have been few cases of fraud.