Donald Trump's acting attorney general has reportedly said Robert Mueller's investigation into possible collusion between the Trump campaign and Russia will continue.

Matthew Whitaker told Republican senator Lindsey Graham the special counsel's probe would proceed, according to a person familiar with the conversation, who spoke to The Associated Press on condition of anonymity.

Mr Trump appointed Mr Whitaker acting attorney general last week, which some critics have said is unconstitutional, since the lawyer has not been senate-confirmed.

The meeting with Mr Graham and Mr Whitaker on Thursday comes as a bipartisan group of senators push for legislation to protect Mr Mueller's job.

The senators are concerned about Mr Whitaker's past criticism of the Mueller investigation, which is also looking at alleged Russian interference in the 2016 election.

Senate Democratic leader Chuck Schumer and other Democrats have called for Mr Whitaker to recuse himself from overseeing the probe.

A Justice Department spokeswoman said earlier this week Mr Whitaker will follow department protocols and consult with senior ethics officials "on his oversight responsibilities and matters that may warrant recusal".

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Democrats have also called for the special counsel bill to be added to a year-end spending bill that must pass in December to avoid a partial government shutdown.

The bipartisan legislation, introduced more than a year ago, would give any special counsel a 10-day window to seek expedited judicial review of a firing and put into law existing Justice Department regulations that a special counsel can only be fired for good cause.

On Wednesday, Republican senator Jeff Flake said he would not vote to confirm judicial nominees unless Republican leaders hold a vote on the Mueller protection legislation.

Trump attacks CNN's Jim Acosta in angry White House press conference Show all 10 1 /10 Trump attacks CNN's Jim Acosta in angry White House press conference Trump attacks CNN's Jim Acosta in angry White House press conference Donald Trump launched an extraordinary tirade against CNN reporter Jim Acosta during a press conference following the midterm elections Reuters Trump attacks CNN's Jim Acosta in angry White House press conference The US president ordered the journalist to put down his microphone and “just sit down” AFP Trump attacks CNN's Jim Acosta in angry White House press conference The row began following a question about the migrant caravan approaching the US, when Mr Trump was asked by CNN’s Jim Acosta if he thought he had “demonised” migrants by calling the group an “invasion” EPA Trump attacks CNN's Jim Acosta in angry White House press conference “I think you should let me run the country, you run CNN, and if you did it well, your ratings would be much better,” said the President AFP/Getty Trump attacks CNN's Jim Acosta in angry White House press conference After Mr Acosta attempted to follow up his question with a second on Robert Mueller’s Russia probe, Mr Trump added, pointing angrily: “That’s enough. That’s enough. That’s enough. Excuse me, that’s enough.” Mr Trump said he was “not concerned about anything” because the investigation was “a hoax”. Continuing to berate Mr Acosta, he added: “That’s enough. Put down the mic.” As the reporter continued to quiz him, Mr Trump became more agitated and stepped away from the podium. EPA Trump attacks CNN's Jim Acosta in angry White House press conference Returning to the podium, Mr Trump said: “I’ll tell you what, CNN should be ashamed of itself having you working for them. You are a rude, terrible person. You shouldn’t be working for CNN REUTERS Trump attacks CNN's Jim Acosta in angry White House press conference Trump continued: 'The way you treat Sarah Huckabee is horrible and the way you treat other people are horrible. You shouldn’t treat people that way.” She was sitting in the room listening on REUTERS Trump attacks CNN's Jim Acosta in angry White House press conference A second reporter, Peter Alexander, was called on by the president and said: “In Jim’s defence I’ve travelled with him a lot, he’s a diligent reporter.” EPA Trump attacks CNN's Jim Acosta in angry White House press conference Mr Trump cut him off, telling the NBC News journalist that “I’m not a big fan of yours either”, prompting laughter in the room AP Trump attacks CNN's Jim Acosta in angry White House press conference Mr Acosta continued to try to ask questions without his microphone, causing Mr Trump to tell him: “Just sit down, please. When you report fake news – no – when you report fake news, which CNN does, a lot, you are the enemy of the people.” REUTERS

Mr Whitaker is now overseeing the Mueller probe, which had previously been overseen by deputy attorney general Rod Rosenstein. Mr Rosenstein told congress he saw no reason to fire Mr Mueller.

Recently ousted attorney general Jeff Sessions had recused himself from overseeing Mr Mueller because he had worked on Mr Trump's Republican campaign and failed to disclose to congress meetings with Russia's ambassador — a decision that infuriated Mr Trump and led to Mr Sessions resigning at the president's request.

Mr Trump has repeatedly criticised Mr Mueller and called the investigation a hoax.

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In a rambling series of tweets which made a number claims without accompanying evidence, Mr Trump wrote: "The inner workings of the Mueller investigation are a total mess.

"They have found no collusion and have gone absolutely nuts. They are screaming and shouting at people, horribly threatening them to come up with the answers they want. They are a disgrace to our Nation and don’t care how many lives the ruin.

"These are Angry People, including the highly conflicted Bob Mueller, who worked for Obama for 8 years. They won’t even look at all of the bad acts and crimes on the other side. A TOTAL WITCH HUNT LIKE NO OTHER IN AMERICAN HISTORY!"