"We are extremely alarmed by management's decision to silence the journalists we represent at Bloomberg Industry Group, as well as the unrepresented journalists at Bloomberg News," wrote the union in a late Monday letter.

"We call on Bloomberg corporate management to rescind its policy and allow journalists throughout the Bloomberg family to do their jobs."

"The Guild believes journalists should not only be allowed - but encouraged - to thoroughly cover every single candidate as the profession demands in one of the most important elections in modern history," the union added. "A journalist's job is, above all, to cover the news and to serve as an independent monitor of power."

The controversial decision announced by editor-in-chief John Micklethwait, was announced last week to the outlet's 2,700 journalists and analysts. They will still cover polls, policies and how the Bloomberg campaign is doing, however investigative stories on Bloomberg or any other Democratic candidate are now banned. They will continue to investigate and report on the Trump administration.