Donald Trump has said the American public "deserves" a federal investigation of Hillary Clinton and the Democratic National Committee over a joint fundraising agreement they signed in August 2015.
The president launched a multi-part Twitter attack criticising his former 2016 rival, writing: "Crooked Hillary bought the DNC & then stole the Democratic Primary from Crazy Bernie!"
He added that it was the "real story on Collusion".
Everybody is asking why the Justice Department (and FBI) isn't looking into all of the dishonesty going on with Crooked Hillary & the Dems..— Donald J. Trump (@realDonaldTrump) November 3, 2017
...New Donna B book says she paid for and stole the Dem Primary. What about the deleted E-mails, Uranium, Podesta, the Server, plus, plus...— Donald J. Trump (@realDonaldTrump) November 3, 2017
....People are angry. At some point the Justice Department, and the FBI, must do what is right and proper. The American public deserves it!— Donald J. Trump (@realDonaldTrump) November 3, 2017
The real story on Collusion is in Donna B's new book. Crooked Hillary bought the DNC & then stole the Democratic Primary from Crazy Bernie!— Donald J. Trump (@realDonaldTrump) November 3, 2017
Pocahontas just stated that the Democrats, lead by the legendary Crooked Hillary Clinton, rigged the Primaries! Lets go FBI & Justice Dept.— Donald J. Trump (@realDonaldTrump) November 3, 2017
Mr Trump's accusation follows Politico's publication of an excerpt from former acting DNC chairwoman Donna Brazile's upcoming book.
Ms Brazile claims she found proof that the 2016 Democratic primary was rigged in Mrs Clinton's favour. Ms Brazile said she believes no laws were violated, but a funding agreement "looked unethical".
Late on Thursday, Mr Trump tweeted - without evidence - that he believed they had acted "illegally".
In subsequent tweets on Friday, he highlighted criticism of the DNC from Massachusetts senator Elizabeth Warren, whom he has mocked by calling her Pocahontas. He also called on federal authorities to launch an investigation.
"Lets go FBI & Justice Dept.," he tweeted.
The fundraising agreement during the primary process was unusual for an open seat and, according to Ms Brazile, gave the Clinton campaign oversight of some DNC decisions.
Months later, Mrs Clinton's chief challenger, independent senator Bernie Sanders, signed his own agreement with the party.
Mr Trump and his campaign are subjects of a wide-ranging investigation by special counsel Robert Mueller.
The White House has repeatedly sought to turn the attention of the probe, which is looking into potential collusion between the Trump team and the Russian government, to Mrs Clinton and her campaign.