Former US President Donald Trump and his family faced the increasing likelihood of criminal charges on May 20 after New York state’s prosecutor said it was working with Manhattan investigators in its probe into the businessman and former reality TV show star’s business dealings.

The office of New York state Attorney General Letitia James announced late on May 18 that it was investigating the Trump Organization in a “criminal capacity”.

Previously, it had said its probe into possible tax, insurance and bank fraud was through civil proceedings, which do not carry the threat of an indictment or imprisonment.

Trump denies wrongdoing and released a statement on May 19 describing the investigation and the parallel criminal probe by Manhattan’s district attorney (DA) as “a continuation of the greatest political witch hunt in the history of the United States”.

The prosecutors in both Manhattan and New York state are Democrats.

James’ spokesman Fabien Levy said: “We have informed the Trump Organization that our investigation into the organisation is no longer purely civil in nature.

“We are now actively investigating the Trump Organization in a criminal capacity, along with the Manhattan DA.”

The Trump Organization is the holding company for hundreds of Trump entities, ranging from hotels to golf courses.

It is not listed on the stock exchange and is therefore not required to report its accounts.

Investigators suspect the organisation may have artificially inflated and reduced the value of assets, particularly several properties in New York state, to either get bank loans or reduce their taxes.

Manhattan DA Cyrus Vance’s investigation initially focused on hush payments made to two women who allege they had affairs with Trump, but has expanded to allegations of tax evasion, and insurance and bank fraud.

Vance, who leaves his post at the end of December, acquired eight years of Trump’s tax returns in February after a years-long legal battle that went to the Supreme Court.

Two state assistant attorneys general will join the Manhattan DA’s efforts, according to sources familiar with the matter cited in The New York Times, as James’s office continues its civil inquiry.

Bennett Gershman, professor of criminal law at Pace University and a former Manhattan deputy attorney, said James’s announcement amounts to a “show of strength” by the two prosecutors.

“They are showing they mean business,” he said. “They are moving forward aggressively. They are not backing off.

“Looking at this announcement I’d say we are much closer to charges being brought,” Gershman added.