Progressive firebrand Sen. Elizabeth Warren said Thursday that she was “troubled” that ex-President Obama will pocket $400,000 for a speech to a top Manhattan investment firm.

“I was troubled by that,” Warren said on SiriusXM’s “Alter Family Politics” while plugging her new book.

“One of the things I talk about in the book is the influence of money. I describe it as a snake that slithers through Washington. And that it shows up in so many different ways here in Washington.”

Obama will get the 400 grand — the same amount he was paid in a year as president — for speaking at Cantor Fitzgerald LP’s health care conference in September, according to reports.

“The influence of dollars on this place is what scares me. I think it ultimately threatens democracy,” the Massachusetts senator said.

“And one of the reasons I feel so urgent when I wrote this book is that we have to think about what the tools are to fight back against it.”

Obama spokesman Eric Schultz said in a statement that the fat speaking fee would not affect the former president’s politics.

“With regard to this or any speech involving Wall Street sponsors, I’d just point out that in 2008, Barack Obama raised more money from Wall Street than any candidate in history — and still went on to successfully pass and implement the toughest reforms on Wall Street since [President Franklin Delano Roosevelt],” Schultz wrote, The Hill reported.