NBC News national political reporter Jonathan Allen said on C-SPAN Thursday that former President Bill Clinton told Democratic National Committee Chairman Tom Perez to not let Sen. Bernie Sanders' (I., Vt.) supporters become powerful in the party.

Allen is the author of Shattered: Inside Hillary Clinton's Doomed Campaign and wrote a book about Clinton's work as secretary of state in 2014.

"The DNC is unpopular with its own base," Allen said. "Roughly half the Democratic Party felt like the DNC was unfairly tipping the scales in the last presidential election trying to get Hillary Clinton nominated trying to hurt Bernie Sanders."

The bad blood between the Clinton and Sanders camps resumed "the minute Donald Trump was elected," Allen claimed.

Earlier this week, Hillary Clinton said that being a capitalist probably hurt her cause in 2016 because so many Democrats in the party today are socialists. The comment appeared to be hit at Sanders who describes himself as a democratic socialist.

She has laid blame on numerous factors for her eventual general election defeat at the hands of President Donald Trump, Sanders and his diehard supporters among them. Sanders ripped Clinton as beholden to Wall Street interests during the primary, and she wrote his attacks did "lasting damage" to her.

Clinton also criticized Sanders as unrealistic in his policies and for essentially offering voters a bill of goods.

Allen said Perez got "very explicit" instructions from Clinton "not to let the party go to the Bernie Sanders folks."

Sanders' 2016 campaign manager Jeff Weaver has lots of issues with the DNC and called it a "fantasy" that Sanders will hand over his voter data to them.

"We’ve also got to make sure that all the different factions of the party are represented at the DNC," Weaver said in January. "Tom can do a little bit more to bring in some other voices."