Sen. Bernie Sanders Wednesday warned president-elect Donald Trump his promises to reform the banking industry and invest in the infrastructure better not be hollow or “we will not only oppose his economic policies, we will expose the hypocrisy.”

In what was billed as a major speech at George Washington University, the Vermont independent who gained a leadership position among Senate Democrats this week, demanded Trump reverse his decision to make Stephen Bannon, who is seen as racist and anti-Semitic, his chief strategist and also lashed out at suggestions he hurt Hillary Clinton’s chance at election.

Sanders pledged to work with the Trump administration on reforming the banking sector and ramping up infrastructure investment.

"If those promises turn out to be hollow …. we will not only oppose his economic policies, we will expose the hypocrisy,” he said.

“The first thing that will be resolved — pretty quickly — is whether or not everything that he was saying to the working families of this country was hypocrisy, was dishonest, or whether he was sincere,” Sanders said. “And we will find that out soon enough.”

On Bannon, who headed the alt-right Breitbart News website, Sanders said the president “should not have a racist by his side." Earlier in the day, Sanders called Bannon’s appointment “totally unacceptable.”

Sanders said Democrats will not help Trump expand bigotry, racism, sexism or xenophobia.

Sanders bristled at the suggestion he hurt Clinton’s presidential campaign, saying he brought millions of new voters into the process.

"You can argue the exact reverse — that maybe I would have been elected president of the United States," Sanders said.

"The presumption behind that question is that we should anoint candidates for president, that a serious debate or candidates competing against each other is a bad thing for democracy."

Throughout the primaries, Sanders criticized Clinton as too close to Wall Street and big business, but ultimately campaigned hard for her, making 21 speeches in 12 battleground states in the last week of the campaign alone.

"Few people in this country worked harder for Hillary Clinton than I did," he said.

Sanders chided Trump over his position on climate change, which the billionaire real estate mogul has called a hoax invented by the Chinese. Sanders said if alternatives to fossil fuels are not found, the planet could become uninhabitable.

“Tell Mr. Trump to read a little bit about science,” he said.

“Climate change is not a hoax. It is the greatest planetary crisis that we face.”