US Senator Bernie Sanders has called for changing the Electoral College, in the wake of the electors' overwhelming vote to seal President-elect Donald Trump’s November 8 victory.

Presidential electors gave Trump 304 votes as they reconvened to cast their ballots on Monday, 34 votes more than the 270-vote threshold he needed to secure the presidency.

Trump’s Democratic rival Hillary Clinton won 227 votes, despite winning the popular vote by a margin of more than 2.5 million.

“We need to change the Electoral College,” tweeted Sanders, who ran a strong campaign against Clinton for the Democratic nomination.

“Trump received 2.5 million fewer votes than Clinton, yet he'll soon be president. Clearly, in a democratic society, this shouldn't happen,” he fumed in a second tweet.

This was not the first time that the Vermont senator was questioning the American way of electing a president into office.

Following Trump’s surprise victory against Clinton, Sanders told CNN that the process was “unfair” and “on the surface a little bit weird” because the former secretary of state was ahead in the popular vote.

“And then what ends up happening is campaigns are basically about 16, 17 states, battleground states, in this country, and I think that's unfair to the other 30-plus states that would also like to be part of the political process,” he said at the time.

Meanwhile, The New York Times, which had officially endorsed Clinton, echoed the senator’s views in an editorial titled “Time to End the Electoral College.”

Donald Trump (L) listens to Hillary Clinton in a pre-election debate.

The Election Day results pointed to a 306-232 win for Trump in the Electoral College.

The projection was engulfed in doubt when some presidential electors started an insider effort to convince other members to break away from Trump and reduce his votes to beneath the required threshold.

However, it was the Clinton camp that saw the most defections as three electors opted for former secretary of state Collin Powell. Sanders and Native American leader Faith Spotted Eagle also received one vote each.

The vote came as Democrats, including President Barack Obama, alleged that Trump had won the White House through Russian support, an allegation denied by both Moscow and the Trump campaign.