President Donald Trump Trump has made an unannounced trip to the Martin Luther King Jr memorial - after being criticised for his empty calendar on the federal holiday.

On Sunday, just hours after vice president Mike Pence compared Mr Trump to the civil rights movement icon, the White House schedule release showed no public events scheduled for Martin Luther King Jr Day.

Reverend Al Sharpton, founder of the National Action Network, blasted the president for his failure to honor the King during a national breakfast event for the civil rights legend.

“This is an insult to the American people that the president of the United States does not officially recognize or give any ceremony for Dr King,” Mr Sharpton said on Monday.

“The White House has not only shut down those workers, they’ve shut down the King holiday,” he added, referring to the nearly month-long government shutdown.

Mr Trump, however, later issued a standard presidential proclamation for on Monday morning, followed by his visit.

"Today we celebrate Dr Martin Luther King, Jr for standing up for the self-evident truth Americans hold so dear, that no matter what the color of our skin or the place of our birth, we are all created equal by God," the president tweeted.

In an interview with CBS, Mr Pence said the president’s decision to shutdown the government over Congress’ refusal to cough up $5bn (£3.9bn) for a border wall on the US-Mexico border is similar to how King attempted to bring about change on race and civil rights in the United States.

“You think of how [King] changed America,” Mr Pence said. “He inspired us to change through the legislative process to become a more perfect union. That’s exactly what president Trump is calling on Congress to do: Come to the table in the spirit of good faith. We’ll secure our border and we’ll reopen the government. And we’ll move our nation forward as the president said yesterday to even a broader discussion about immigration reform in the months ahead.”

This isn’t the first time the White House has used a King comparison. Last year, former presidential aide Steve Bannon said the civil rights hero would have loved Mr Trump.

A civil rights group is also invoking Martin Luther King Jr’s legacy to hold Mr Trump accountable to his promise of proposing a national ID card. Two years ago, the Drum Major Institute, a civil rights group co-chaired by Martin Luther King III, met with the president and discussed creating national ID cards to remove obstacles to voting and eliminate opportunities for voter suppression. Mr Trump, who was president-elect at the time, endorsed the national ID proposal.

Now, the group is making sure Mr Trump follows through on that promise.

“We want to make sure that no voter is left behind because of the inability to get a photo-id,” William Wachtel, co-founder of Drum Major Institute, told The Hill. “Most people spend their time fighting over who’s trying to keep people from not voting as opposed to finding solutions to make it possible for everyone to vote. That’s why Dr King fought so hard for the Voting Rights Act.”

As of 2018, about 17 states require a photo ID from citizens in order to vote in elections.