February 23, 2017 0930 GMT
During a private lunch meeting with a bipartisan group of 10 senators on Thursday, Trump reportedly suggested that he and Republican Senator Kelly Ayotte would have won New Hampshire in the November elections if not for the “thousands” of people who were “brought in on buses” from neighboring Massachusetts to “illegally” vote in the battleground state.
Trump received 46.5 percent of the vote in New Hampshire, while Democratic nominee Hillary Clinton won 46.8 percent and carried the state's four electoral votes.
Like Trump, Sen. Ayotte suffered a narrow defeat in New Hampshire.
A member of the Federal Election Commission is now calling on Trump to share any evidence he has to support his claim.
"The president has issued an extraordinarily serious and specific charge. Allegations of this magnitude cannot be ignored," FEC Commissioner Ellen Weintraub said in a statement on Friday.
Trump’s claim would mean that thousands of people voted illegally in the state, which is a felony under New Hampshire law.
It is not the first time Trump has made allegations of voter fraud without presenting evidence. In a meeting with members of Congress last month, the president claimed that 3 to 5 million voted illegally in the 2016 election, causing him to lose the popular vote to Clinton.
As a candidate, Trump also repeatedly raised the specter of widespread voter fraud during early voting across the country.
On Election Day, Trump accused the media of ignoring “serious voter fraud” in California, New Hampshire and Virginia.
The outcome of the November vote has also been questioned by Democrats, who have blamed their defeat on foreign influence, particularly on the alleged Russian intervention in the election in favor of Trump.