Exclusive: US presidential hopeful Donald Trump signed off on a controversial business deal that was designed to deprive the American government of tens of millions of dollars in tax, the Telegraph can disclose.

The billionaire approved a $50 million investment in a company – only for the deal to be rewritten several weeks later as a ‘loan’.

Experts say that the effect of this move was to skirt vast tax liabilities, and court papers seen by the Telegraph allege that the deal amounted to fraud.

Independent tax accountants and lawyers said that the documents Mr Trump signed – copies of which were obtained by this newspaper as part of a three-month investigation - contained “red flags” indicating the deal was irregular.

But the Republican presumptive presidential nominee signed nonetheless.