• The New York Attorney General's office suggested that the Trump Organization failed to produce evidence in the $250 million fraud trial of Donald Trump and his company.
• The office cited a report accusing former Trump CFO Allen Weisselberg of lying under oath.
• The AG's office proposed that an independent monitor conduct a forensic review of electronic data held by the Trump Organization.

New York Attorney General Letitia James' office suggested Thursday that the Trump Organization failed to produce evidence in the $250 million fraud trial of Donald Trump and his company, citing a recent report accusing a key witness of lying under oath.

The AG's office said in a letter that it has "identified likely omissions" in documents produced by the defendants related to 2016 exchanges with Forbes Magazine about the value of Trump's real estate assets.

That alleged failure "indicates a breakdown somewhere in the process," an official from that office warned the judge who will deliver verdicts in the ongoing civil trial.

It is "also suggestive of potentially broader issues in the production process," wrote the official, senior enforcement counsel Kevin Wallace, in the letter to Judge Arthur Engoron.

The accusation cuts against Trump's repeated claim that all of the witness testimony in the trial is "perfect for us." And it could undermine the defense of former Trump Organization chief financial officer Allen Weisselberg, who has been accused of lying on the stand in an effort to distance himself from false financial statements at the heart of the case.

The attorney general's suit accuses Trump, his sons Donald Trump Jr. and Eric Trump, the Trump Organization and top executives of misstating the true values of properties to obtain tax advantages and better terms on loans and insurance. James wants the court to levy $250 million in damages and permanently bar Trump and his two adult sons from serving as officers of any New York business.

Wallace, in his letter, proposed that an independent monitor conduct a forensic review of electronic data held by the Trump Organization from August to September 2016.

"If the Monitor determines that responsive information was not produced, she can provide an assessment of where in the process the failure occurred and propose remedies to ameliorate those issues," Wallace wrote.

The letter cites a Forbes article accusing Weisselberg of lying during his sworn testimony last week in the civil trial in Manhattan Supreme Court.

The article, titled "Trump’s Longtime CFO Lied, Under Oath, About Trump Tower Penthouse," said Weisselberg falsely claimed on the stand that he had "never focused" on the valuation of Trump's apartment.

But Forbes, which has long tracked the wealth of the world's richest people, said that Weisselberg's claim is not true.

"A review of old emails and notes, some of which the attorney general's office does not possess, show that Weisselberg absolutely thought about Trump's apartment — and played a key role in trying to convince Forbes over the course of several years that it was worth more than it really was," Forbes wrote. 

The article went on, "Given the fact that these discussions continued for years, and that Weisselberg took a very detailed approach in reviewing Trump's assets with Forbes, it defies all logic to think he truly believes what he is now saying in court."

Wallace noted in Thursday's letter that the defendants have "produced some documents reflecting ongoing exchanges with Forbes Magazine about the valuation of assets during August and September 2016."

Weisselberg as part of those exchanges had obtained financial information about the company's golf courses, Wallace wrote.

But he added, "While Defendants have produced some emails in that exchange, it appears they have not produced a later set of emails" between Weisselberg and a real estate expert, Steven Ekovich.

The alleged failure to produce those emails follows "multiple affidavits on behalf of the Trump Organization attesting to the completion of their production obligations," Wallace wrote.

He suggested an Oct. 27 deadline for the monitor to submit a report on the forensic examination.

Trump, who has attended five days of the trial, and his co-defendants have denied wrongdoing.

Engoron has already ruled that they are liable for fraud. The trial will settle six related claims alleged by James.

Attorneys for Trump and Weisselberg did not immediately respond to CNBC's request for comment. Weisselberg, who has been loyal to Trump, served jail time for tax fraud in a criminal case related to his work at the Trump Organization.

Forbes removed Trump from its ranking of the 400 richest people in the U.S. earlier this month, alleging his current estimated net worth of $2.6 billion was down more than $600 million from a year ago.

James alleged in September that Trump overstated his net worth by up to $3.6 billion each year.