Allen Weisselberg, the chief financial officer for the Trump Organization, has surrendered to New York authorities ahead of criminal charges expected to be announced later on Thursday against him and the former president’s company.

The anticipated charges mark a decisive turn in a nearly three-year investigation of Donald Trump’s business by Cyrus Vance, the Manhattan district attorney, in tandem with New York attorney-general Letitia James.

They concern fringe benefits paid to Weisselberg and other top executives for things such as private school tuition, car leases and apartment rent, according to people briefed on the matter. Lawyers involved in the case were waiting for the charges to be unsealed later in the day to see the precise details of the case.

The Trump Organization issued a blistering statement, accusing prosecutors of using Weisselberg, “a loving and devoted husband, father and grandfather”, as “a pawn in a scorched earth attempt to harm the former president”.

“This is not justice; this is politics,” it added.

Lawyers for Weisselberg, 73, said he “intends to plead not guilty and he will fight these charges in court.” He reportedly entered the court complex through a back entrance early on Thursday morning. The Manhattan DA and the attorney-general did not comment.

Trump is not expected to be charged, nor are his three adult children who have served as senior executives at the Trump Organization: Donald Jr, Ivanka and Eric. Trump has repeatedly derided the investigation as a witch-hunt perpetrated by his political foes. Both Vance and James are Democrats.

The former president’s lawyers had tried in recent days to persuade prosecutors to stand down. As it became clear Vance and James were moving towards charges, a lawyer for Trump, Ronald Fischetti, promised a vigorous defence.

“In my more than 50 years of practice, never before have I seen the district attorney’s office target a company over employee compensation or fringe benefits,” Fischetti said last week.

In recent months, Weisselberg has become a focus of prosecutors, who hoped to convince the man who once described himself as Trump’s “eyes and ears” to aid their investigation into a private business that features hundreds of byzantine partnerships.

The former president’s business was already struggling, with revenue falling at some of its hotels and golf courses due to the coronavirus pandemic. Some partners such as the Professional Golfers’ Association have cut ties in protest at his role in the January insurrection at the US Capitol.

The Trump Organization has about $900m in debts coming due over the next four years, about a third of which are personally guaranteed by Donald Trump.

Vance, who leaves office at the end of this year, will have to hand any case on to a successor. His current probe has been overshadowed by criticism for dropping a previous investigation of the Trump Organization, in 2012, which stemmed from condominium-buyer complaints that Donald Jr and Ivanka had misled them. The parties later settled.

Vance launched the current investigation in 2018 in response to reports that Trump’s former fixer, Michael Cohen, had made hush-money payments to two women who claimed to have had extramarital affairs with the-then presidential candidate. Cohen later told Congress he arranged with Weisselberg to be reimbursed by the Trump Organization through monthly payments listed as legal fees.

The investigation expanded to consider possible bank and insurance fraud, according to court filings. Under examination is whether the Trump Organization inflated the value of certain properties to secure bank loans and insurance while minimising them for tax purposes, according to people briefed on the matter.

The investigation had been hampered by Trump’s refusal to hand over tax records. Vance prevailed in a legal fight that went to the Supreme Court and ultimately took possession of the documents in February.