THE stakes have been raised.

Amid the growing political crisis in Washington, the US Justice Department has appointed a Special Counsel to oversee its investigation into Russia's interference in the 2016 election.

Robert S. Mueller, a former director of the FBI, will now be in charge of the investigation, which is also looking into potential collusion between members of Donald Trump's campaign team and the Russian government.

Why would a Special Counsel be needed? It's all about independence. Mr Mueller comes from outside the Justice Department, which means he is able to conduct the investigation without raising any conflicts of interest with department employees.

"I determined that it is in the public interest for me to exercise my authorities and appoint a Special Counsel to assume responsibility for this matter," the Deputy Attorney General, Rod Rosenstein, said in a statement announcing the move.

"My decision is not a finding that crimes have been committed or that any prosecution is warranted. I have made no such determination."

"If the Special Counsel believes it is necessary and appropriate, the Special Counsel is authorised to prosecute federal crimes arising from the investigation," it says.

The Justice Department has told NBC News the White House was informed of Mr Rosenstein's decision only after he signed the order.