Rep. Peter Welch (D-Vt.) apologized Tuesday for a tweet in which he claimed that the partial government shutdown marks the first time in U.S. history that people have legally been made to work without pay. (Alex Brandon/AP/file)

Rep. Peter Welch (D-Vt.) apologized Tuesday for a tweet in which he claimed that the partial government shutdown marks the first time in U.S. history that people have legally been made to work without pay.

The tweet prompted a rebuke from critics who pointed out that Welch was neglecting America’s long history of slavery.

“Never in the history of this country has it been legal to make people work for free but that’s what’s happening to federal employees. This can never happen again,” Welch said in his initial tweet early Tuesday night.

In the tweet, Welch shared a link to a story about legislation he has introduced that would immediately provide back pay to federal workers who have been required to work during the partial shutdown, now in its 32nd day.

Welch sent a follow-up tweet later Tuesday in which he apologized for his statement.

“Sincere apologies,” he said in the tweet. “Nothing worse in the history of our country than the brutal inhumanity of the horrible, relentless, and savage infliction of involuntary servitude-slavery- on millions of people whose freedom was denied. Nothing.”