The US Supreme Court has cleared the way for eight years of Donald Trump’s tax returns to be turned over to a New York prosecutor who is investigating him.
In response, Mr Trump claimed he was a victim of "fascism" and "continuing political persecution".
He said "headhunting" Democrat prosecutors were "using the law as a weapon" against him.
In a statement on Monday, the former president said: "It just never ends! That’s what is done in third world countries. That’s fascism, not justice."
Referring to the election, he added that "many people, and experts, feel that I won. I agree!"
It came as Mr Trump looked set to position himself as the presumptive Republican nominee for 2024 in a speech at a conservative conference in Florida this week.
The former president has been fighting a protracted legal battle to prevent his tax records being obtained by Cyrus Vance, the Manhattan District Attorney.
Mr Trump has called it "a fishing expedition" and "a continuation of the greatest witch hunt in history."
Two years ago Mr Vance, a Democrat, subpoenaed the tax records from Mazars USA, the accounting firm that has long done work for Mr Trump and his businesses.
He has disclosed little about what prompted him to request the tax records.
However, in a court filing last year, prosecutors said they were justified in doing so because there were public reports of "possibly extensive and protracted criminal conduct at the Trump Organization."
The investigation is known to have originally centred on "hush money" payments to adult film actress Stormy Daniels and Playboy model Karen McDougal during the 2016 presidential campaign.
Both women claimed to have had sexual encounters with Mr Trump, which he denied.
In recent court filings, Mr Vance has suggested it is now broader and could focus on potential bank, tax and insurance fraud.
His investigators have interviewed Michael Cohen, Mr Trump's former personal lawyer, who received a three-year prison sentence for making the payments to Ms Daniels and Ms McDougal.
Mr Cohen testified to Congress that Mr Trump and his company artificially inflated and devalued the worth of their assets to obtain bank loans and reduce taxes.
Mr Trump subsequently accused Mr Cohen of committing "perjury on a scale not seen before."
Investigators also reportedly recently interviewed employees of Deutsche Bank, which has long backed the former president and the Trump Organization with loans.
Following Mr Vance's subpoena in 2019 Mr Trump attempted to block the release of the tax documents, which cover 2011 to 2018.
Last July, the Supreme Court rejected Mr Trump's argument that he was immune from investigation while he held office.
Mr Trump went on to argue he was a victim of political harassment, but the Supreme Court has now rejected his case. In a three-word statement following the ruling, Mr Vance said: "The work continues."
Mr Trump did not immediately respond.
US presidents are not required by law to release details of their taxes, but every leader since Richard Nixon has done so.
In September the New York Times obtained "tax-return data" for Mr Trump stretching over a period of more than two decades.
It reported that Mr Trump paid just $750 in federal income taxes in 2016, the year he won the US presidency, and the same in 2017, his first year in the White House.
The newspaper also reported that Mr Trump paid no federal income taxes in 11 of the 18 years it was able to scrutinise, due to losses made in his businesses.
Mr Trump dismissed the report as "totally fake news".
He will make his first post-presidential speech at the Conservative Political Action Conference this weekend.
The former president dominates polls for the 2024 Republican nomination and his popularity remains high among Republican voters.
Aides said his appearance would be a show of force designed to demonstrate he is still in charge of the party and its direction.