Bernie Sanders speaks at an anti-'Trumpcare' rally in Washington, DC on May 4. Alex Wong/Getty Images Bernie Sanders, the liberal Vermont senator and former presidential candidate, pressed for a dramatically more progressive Democratic Party platform in a Wednesday New York Times op-ed titled, "How Democrats Can Stop Losing Elections."

Sanders, who gained an unexpectedly large and loyal following in the 2016 Democratic presidential primary, argued that the party is at a "pivotal" turning point in which it must appeal to young and working class voters in order to expand its ranks.

"For the sake of our country and the world, the Democratic Party, in a very fundamental way, must change direction," he wrote.

The senator pointed to the recent election in the UK, in which the liberal Labour party made significant and unexpected gains over the ruling conservative party, and drew large turnout among young voters. He attributed Labour's renewed popularity to its very progressive policy platform, which is similar to the one Sanders is promoting in the US.

"The British elections should be a lesson for the Democratic Party," he wrote.

Hillary Clinton's surprising loss in November, Sanders argues, reflects the failure of moderate politics funded by big money donors.

Rather than staking out a middle ground as a way of appealing to Trump sympathizers and independents, he says the party should challenge the administration's positions with policy solutions radical enough to attract Americans who have "given up on democracy."

"While Democrats should appeal to moderate Republicans who are disgusted with the Trump presidency, too many in our party cling to an overly cautious, centrist ideology," he wrote. "The party's main thrust must be to make politics relevant to those who have given up on democracy and bring millions of new voters into the political process."

Sanders says Democratic candidates should run on Medicare-for-all, "accelerate" their efforts to promote renewable and efficient energy use, and challenge corporate interests.

"If the Democrats are prepared to rally grass-roots America in every state and to stand up to the greed of the billionaire class, the party will stop losing elections," he concluded.