Bernie Sanders has issued a passionate rallying call to Democrats on the day Donald Trump was sworn in as 45th President of the United States.

The Vermont senator, who ran against Hillary Clinton for the Democratic presidential nomination, declared “we are not giving up” in a short video published on his Twitter page.

Speaking ahead of the inauguration ceremony, he said: “Today is going to be a tough day for millions of Americans, including myself. But our response has got to be not to throw up our hands in despair, not to give up, but in fact to fight back as effectively and as vigorously as we can.

“Our job is to keep our eyes on the prize. And the prize is that we will continue fighting for a government that represents all of us, not just the one per cent.

“We’re going to go forward in the fight for economic, social, environmental and racial justice. That’s who we are, that’s what we’re gonna do. We are not giving up.”

Mr Trump was sworn in as President during a ceremony in Washington DC on Friday afternoon.

His inaugural address contained many of the messages he had promoted during the presidential campaign, including promises to “make America great again”, put “America first” and "eradicate Islamic terrorism".

Trump Inauguration protests around the World Show all 14 1 /14 Trump Inauguration protests around the World Trump Inauguration protests around the World Activists from Greenpeace display a message reading "Mr President, walls divide. Build Bridges!" along the Berlin wall in Berlin on January 20, 2017 to coincide with the inauguration of Donald Trump as the 45th president of the United State Getty Trump Inauguration protests around the World An activist holds up a sign at the "We Stand United" rally on the eve of US President-elect Donald Trump's inauguration outside Trump International Hotel and Tower in New York on January 19, 2017 in New York Getty Trump Inauguration protests around the World Protesters burn a U.S. flag and a mock flag with pictures of U.S. President-elect Donald Trump outside the U.S. embassy in metro Manila, Philippines Getty Trump Inauguration protests around the World Filipino protestors hold placcards during a protest rally in front of the US embassy in Manila, Philippines, 20 January 2017. On the eve of President-elect Donald Trump's inaguration as the 45th president of the United States, Filipinos and Fil-Americans held a protest in front of the US embassy in Manila to denounce the incoming US president. Getty Trump Inauguration protests around the World Hong Kong police officers and security guards look on as an anarchist protester belonging to the Disrupt J20 movement sits after using a heavy duty D-lock and motorcycle lock to chain himself to a railing at the entrance gate to the Consulate General of the United States of America in Hong Kong to protest the inauguration of United States President-elect Donald Trump, Hong Kong, China, 20 January 2017. Two activists were arrested and taken away by Hong Kong police during the demonstration. Getty Trump Inauguration protests around the World A banner is unfurled on London's Tower Bridge, organised by Bridges Not Walls - a partnership between grassroots activists and campaigners working on a range of issues, formed in the wake of Donald Trump's election, which aims to build bridges to a world free from hatred and oppression. Getty Trump Inauguration protests around the World Protesters chain themselves to an entry point prior at the inauguration of U.S. President-elect Donald Trump in Washington, DC, U.S. Getty Trump Inauguration protests around the World Bridges Not Walls banner dropped from Molenbeek bridge in Brussels, Belgium, 20 January 2017, in an Greenpeace action part of protests Wolrd protest in solidarity with people in the US, the day Donald Trump sworn in as the 45th President of the United States. Getty Trump Inauguration protests around the World A woman holds an anti-U.S. President-elect Donald Trump placard during a rally in Tokyo, Japan, Getty Trump Inauguration protests around the World A Palestinian protester holds a placard during a demonstration against the construction of Jewish settlements in the occupied West Bank and against US President-elect Donald Trump, on January 20, 2017, near the settlement of Maale Adumim, east of Jerusalem Getty Trump Inauguration protests around the World Banners on North Bridge in Edinburgh as part of the Bridges Not Walls protest against US President Donald Trump on the day of his inauguration Getty Trump Inauguration protests around the World Russian artist Vasily Slonov (L) and his assistant carry a life-sized cutout, which is an artwork created by Slonov and titled "Siberian Inauguration", before its presentation on the occasion of the inauguration of U.S. President-elect Donald Trump, in a street in Krasnoyarsk, Russia Getty Trump Inauguration protests around the World A woman holds a banner during a march to thank outgoing President Barack Obama and reject US President-elect Donald Trump before his inauguration at a park in Tokyo, Japan, 20 January 2017. EPA Trump Inauguration protests around the World Palestinian demonstrators protesting this week against a promise by Donald Trump to re-locate the US embassy to Jerusalem Reuters

Mr Sanders, who has already been tipped to run for president again in 2020, is a member of the Senate Democrat’s leadership group that will be tasked with holding Donald Trump and the Republican majority in Congress to account.

He has been one of the most vocal criticsof the new president since the Republican’s election victory last November.

Earlier this month he took a giant print-out of one of Mr Trump’s tweets to a debate in the Senate. The tweet contained the Republican’s promise not to cut social security payments or the Medicare and Medicaid health programmes.

Mr Sanders used the printout during a debate on the Affordable Care Act, commonly referred to as Obamacre, which the Republicans and Mr Trump now hope to scrap.