The plan does not match the "standards" of US presidents over the last 40 years, Walter Shaub said.

A Trump lawyer said earlier the new trust would face "severe restrictions" on new deals.

But Mr Shaub said the plan would not remove conflicts of interest.

"Every president in modern times has taken the strong medicine of divestiture," he said, referring to a process whereby Mr Trump would sell off his corporate assets and put the profits into a blind trust run by an independent trustee.

At a news conference on Wednesday, lawyer Sherri Dillon said that management of the Trump Organization would be transferred to a trust controlled by Mr Trump's sons Don and Eric and chief financial officer Allen Weisselberg.

The Trump Organization is an umbrella company for Donald Trump's hundreds of investments in real estate, brands and other businesses.