The top Democrat on the Senate Finance Committee is accusing the Treasury Department of refusing to provide documents and information related to President Donald Trump's longtime lawyer Michael Cohen.

The documents Sen. Ron Wyden is seeking are related to Cohen's dealings with the Swiss pharmaceutical company Novartis.

The top Democrat on the Senate Finance Committee is accusing the Treasury Department of refusing to provide documents and information related to President Donald Trump's longtime lawyer and his relationship with the Swiss drug company Novartis.

Democratic Sen. Ron Wyden of Oregon said through a representative on Wednesday that the Treasury Department was not cooperating with his May request for information on Michael Cohen and his dealings with Novartis.

"Treasury refuses to respond to our request, let alone provide key financial documents related to Cohen and Cohen's business dealings with Novartis. There is no excuse for this kind of stonewalling," the representative, Rachel McCleery, said. "All other parties are engaging in the Committee's inquiry."

Last month, Michael Avenatti, the attorney for the adult-film actress Stormy Daniels, released information about Cohen's financial dealings. The information stemmed from Suspicious Activity Reports filed with the Treasury Department showing that companies paid Cohen lucrative sums in exchange for his advising services following the 2016 presidential election.

Cohen had aggressively pitched himself to companies as someone who could get them what they wanted from Trump, but the companies revealed to have worked with him were often disappointed. Cohen did not disclose any of the payments.

Among those companies was Novartis, which paid Cohen more than $1 million through his company Essential Consultants LLC, the same vehicle Cohen used to facilitate the $130,000 hush-money payment to Daniels in October 2016 to keep her quiet about her allegations of a 2006 affair with Trump.

The New Yorker spoke last month with the government official who is said to have leaked the documents. The official said they did so because others were missing from the database of the Treasury Department's Financial Crimes Enforcement Network, known as FinCen.

A FinCen representative released a statement saying that "under longstanding procedures," the office "will limit access to certain" Suspicious Activity Reports "when requested by law enforcement authorities in connection with an ongoing investigation."

The Treasury Department's inspector general announced it was investigating whether someone internally leaked the documents to Avenatti and others.

In May, Wyden sent the letter to FinCen requesting the Suspicious Activity Reports tied to Cohen's firm and Novartis. Wyden has said he is considering blocking additional nominees to the department. Already, he has blocked one nominee as part of a standoff related to document requests involving Russia.

A Treasury spokesman told ABC News that the department doesn't discuss specific requests related to committee investigations.

Cohen is the focus of a criminal investigation in the Southern District of New York into whether he violated campaign-finance laws or committed bank fraud.