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.
Simpson's political intelligence firm commissioned a dossier into Trump's Russian Federation ties, and Republicans have used Simpson as a cudgel against the probe into the White House, saying that it helped spur the investigation and should be discredited.
Fusion GPS hired former British spy Christopher Steele to produce the report, of which the main claims have been unverified.
President Donald Trump on Wednesday was critical of "sneaky" Feinstein.
Feinstein's release was not illegal because the information wasn't classified.
Feinstein's decision to make the transcript public came under fire from top Republican leaders, including Sen.
Feinstein, the committee's ranking Democrat, went against the wishes of the panel's chairman, Sen.
"The innuendo and misinformation circulating about the transcript are part of a deeply troubling effort to undermine the investigation into potential collusion and obstruction of justice", the California Democrat said in a statement. Grassley said he was "confounded" by the release and argued that it could undermine attempts to get additional witnesses. He says she released the testimony "totally without authorization".
Trump has dismissed the information contained in the dossier, which was handed over to the Federal Bureau of Investigation by former MI6 agent Christopher Steele in September 2016. And in deep blue, Democrat-dominated California, that's just the kind of image Feinstein wants to cultivate as she seeks to win yet another term this fall. Two months later, at the FBI's request, Steele gave a more in-depth briefing to bureau officials at a meeting in Rome. 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.
Papadopoulos pleaded guilty in October to lying to the Federal Bureau of Investigation about his conversations with Russian officials, and is cooperating with prosecutors led by special counsel Robert S. Mueller III.