As well as alleging massive tax fraud committed through various deals, the complaint details how Felix Sater, a Russian former business associate of Mr Trump who helped source the FL deal, had previously been convicted of a mob-organised stock fraud heist of Wall Street.

Mr Sater's conviction was reportedly kept hidden when he became an informant for the Federal Bureau of Investigation. It is said he helped secure the arrest of some 19 colleagues to avoid prison time.

Mr Kriss’ lawsuit was suspended when a judge ruled Mr Oberlander's complaint be sealed for revealing Mr Sater's status as an informant. But last month a Manhattan judge reversed the ruling, allowing a version of the complaint to be made public.

The allegations in that complaint are now included in The People of the State of New York ex rel. the Bayrock Litigation Partnership v. Bayrock et al. which is being civilly prosecuted under New York’s qui tam law.

That statute authorises a whistleblower to bring the case in place of the state after the state’s attorney general has investigated and declined to participate in the case. The case is now being brought forward by Mr Oberlander and Richard Lerner, his colleague.

Mr Lerner said: “Mr Trump gave his consent to the transaction after receiving a full set of documentation which made clear that without it the deal would not go through. The extent of his involvement and any culpability will become clear during the course of the case. At this time, it seems that he benefited indirectly as a partner alongside Sater and Bayrock.”