Hillary Clinton's popular vote lead over Donald Trump is continuing to grow, with the possibility that she could gain up to 5 million more votes than the president-elect.

Votes are still being counted in states including California and Michigan, with Clinton currently leading the popular vote by almost 2 million, USA Today reported.

However, even if Clinton earned enough votes in Michigan to actually win the electoral votes there, Trump would still have 290 electoral votes to Clinton's 232, raising to 248 if Michigan was included.

There are currently 12,000 votes between Trump and Clinton in Michigan, where the president-elect has thus far retained a lead.

In California, where an influx of postal votes cast before 8 November are still being counted, Clinton's lead will not make a difference to the outcome of the election, as she already has the 55 electoral votes from the state.

However, should Clinton's lead increase further, calls for changes to the US voting system could continue.

The Electoral College, which sees each state allocated a certain amount of votes dependent on the size of its population, has been criticised by some voters who do not feel they are given adequate representation.

The vote will not become official until the Electoral College convenes on 19 December, and the 538 members cast their votes - with a petition launched to ask the EC to vote for Clinton rather than Trump.

However, Clinton supporters are set for disappointment if they expect a change in the overall outcome of the vote, as Trump's 290 electoral votes far exceed any votes Clinton could gain in the states still counting their ballots.

Following the outcome of the presidential election — which surprised pundits and voters alike — many people in major cities including Los Angeles and New York protested against Trump's win, carrying banners reading 'not my president'.

But Trump has pledged to unite the country, with his transition process including holding consultations with politicians who directly opposed him during his presidential election campaign.