Michael Cohen works as a lawyer for President Donald Trump.Photo: REUTERS
US President Donald Trump's top lawyer is under criminal investigation, the US justice department has announced.
Prosecutors say they are focusing on Michael Cohen's business dealings rather than his work as a lawyer.
Mr Cohen has been under investigation for months, the court filing says.
The filing was in response to efforts by Mr Cohen's own lawyer to stop prosecutors reviewing material seized from Mr Cohen's office on Monday.
Mr Cohen's team argues that the papers are covered by the attorney-client privilege.
President Trump has condemned the office raid, calling it "disgraceful" and "an attack on our country".
During a court hearing in New York on Friday, prosecutor Tom McKay accused Mr Cohen of trying to use attorney-client privilege "as a sword to challenge the government's ability to review evidence".
Government prosecutors also said they believed Mr Cohen had "a low volume of potentially privileged communication" because he seems to only have one client - President Trump.
"It is neither apparent that Cohen, in his capacity as an attorney, has many, or any, attorney-client relationships other than with President Donald Trump," the filing said.
It added that while Mr Cohen was an attorney, "he also has several other business interests and sources of income", and is "being investigated for criminal conduct that largely centres on his personal business dealings".
A new lawyer for President Trump, Joanna Hendon, said the president had an "acute interest" in the case. Ms Hendon, who was hired on Wednesday, asked the judge to adjourn the session so she had more time to prepare.
According to a New York Times report, the president phoned Mr Cohen to "check in" on him today.
Lawyers tend to advise clients not to discuss investigations - which means their discussion could cause them problems, depending on what they talked about.
In a separate development, Mr Cohen reportedly negotiated a $1.6 million settlement with a former Playboy model on behalf of a Republican fundraiser, according to a Wall Street Journal article.
Elliott Broidy, a Los Angeles investor, acknowledged "a consensual relationship" with the Playmate, who became pregnant.
Mr Broidy said it was "unfortunate" that the personal matter was "the subject of national discussion" because of the involvement of Mr Cohen.
The investor was previously in the news after he urged President Trump to sack then-Secretary of State Rex Tillerson over a diplomatic dispute.
Mr Cohen has admitted to have paid a porn actress, Stormy Daniels, $130,000 before the 2016 US presidential election.
Ms Daniels claims she had an affair with Mr Trump, and he and his lawyers made attempts to buy her silence.
The president denies the alleged relationship.