The former IRS contractor accused of leaking former President Donald Trump's tax returns and stealing tax information on thousands of the wealthiest people in the US pleaded guilty in federal court on Thursday.

Prosecutors say Charles Littlejohn of Washington, DC, sent Trump's tax returns and other data to two media outlets that "published numerous articles describing the tax information they obtained from the Defendant."

Littlejohn pleaded guilty to the one count of disclosing tax information, which he was charged with in late September.

The contractor's crime affected so many individuals that prosecutors plan to create a public website to notify the victims of any developments in the case.