Dianne Feinstein for releasing the transcript of an interview with the co-founder of a political opposition firm that commissioned a dossier of allegations about Trump's presidential campaign and Russian Federation.
He went on to call for Feinstein to face a "tough" primary challenge in her 2018 reelection campaign.
Trump's statement follows lawsuits filed by his personal lawyer against BuzzFeed over the publication of the dossier and against Fusion GPS, the intelligence firm behind the infamous document.
The FBI opened its investigation in July 2016, the same month that Christopher Steele, a former British spy hired by Fusion GPS to write the Trump Dossier, talked to the FBI.
Fusion GPS, which was hired first by Republicans and later Democrats, studied various aspects of Trump's background, a typical function for opposition researchers during presidential campaigns.More news: Tennessee pastor apologizes for asking teen to engage in sexual contact
Dianne Feinstein is learning what it's like to be on the receiving end of President Trump's fury.
"It's totally confounding that Senator Feinstein would unilaterally release a transcript of a witness interview in the middle of an ongoing investigation - a witness that Feinstein herself subpoenaed past year for lack of cooperation", Grassley's press secretary said in a statement.
The lengthy transcript was released over the objections of Republicans, who have been sharply critical of Simpson's firm, Fusion GPS.
Feinstein's decision to make the transcript public came under fire from top Republican leaders, including Sen. Republican Sens. Charles E. Grassley (Iowa), committee chair, and Lindsey O. Graham (S.C.), also on the committee with Feinstein, have referred Simpson for criminal prosecution. He says she released the testimony "totally without authorization".
The criminal referral urged the DOJ to examine whether Steele made false statements to the Federal Bureau of Investigation "about the distribution of claims" contained in the dossier.
The California Democrat rebuked Trump's tweet suggesting that she broke the law by releasing Simpson's testimony. It may have been Trump campaign aide George Papadopoulos, who told an Australian diplomat that Russian Federation had "political dirt" on Hillary Clinton in May 2016, according to The New York Times.