A senior justice department ethics official has concluded acting attorney general Matthew Whitaker should recuse himself from overseeing Robert Mueller's probe examining Donald Trump – but advisers recommended the opposite and he has no plans to step aside, people familiar with the matter said.

Earlier on Thursday, a different official, who spoke on the condition of anonymity, said ethics officials had advised Mr Whitaker need not step aside, only to retract that description of events hours later.

The advice to stay away from the Mueller probe underscores the high stakes and deep distrust – within Congress and in some corners of the justice department – surrounding Mr Whitaker's appointment as the nation's top law enforcement official until the Senate votes on the nomination of William Barr to take the job.

Mr Whitaker did not return messages seeking comment.

Late on Thursday, the justice department formally notified Congress of Mr Whitaker's decision not to recuse himself, writing in a letter that while an ethics official felt he should do so to avoid the appearance of a conflict, that official could not identify a precedent for such a recusal.

Senator Minority Leader Charles Schumer said in a statement Mr Whitaker's refusal to recuse "is an attack on the rule of law and the American justice system, but it is undoubtedly consistent with what President Trump wanted – an unethical yes-man who will do his bidding rather than do what's right".

Within days of the president's announcement in early November that he had put Mr Whitaker in the role on a temporary basis, Mr Whitaker tapped a veteran US attorney to become part of a four-person team of advisers on his new job, according to a senior justice department official.

Their guidance included the question of whether Mr Whitaker should recuse himself from Mr Mueller's investigation because of his past statements regarding that probe and because of his friendship with one of its witnesses, the official said.

Mr Whitaker never asked justice department ethics officials for a formal recommendation, nor did he receive one, this official said.

However, after Mr Whitaker met repeatedly with justice department ethics officials to discuss the facts and the issues under consideration, a senior ethics official told the group of advisers on Tuesday that it was a "close call" but Mr Whitaker should recuse himself to avoid the appearance of a conflict of interest, the official said. Mr Whitaker was not present at that meeting, they said.

Those four advisers, however, disagreed with the ethics determination and recommended to Mr Whitaker the next day not to recuse, saying there was no precedent for that, and doing so now could create a bad precedent for future attorneys general.

When Eric Holder became the attorney general in 2009, he decided to recuse himself from overseeing the investigation of former presidential candidate John Edwards to avoid the appearance of a conflict. Mr Holder's reasoning was he had been part of Barack Obama's vice-presidential search committee that considered Mr Edwards. In that case, Mr Holder did not consult justice department ethics officials before deciding to recuse.

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The senior official who described the Whitaker discussions refused to identify the justice department employees involved. Representative Jerrold Nadler, incoming chairman of the House Judiciary Committee, said in a statement he was troubled by how the information was made public.

"It is simply unacceptable that we are learning about this guidance through leaks to the press instead of from the Acting Attorney General himself," Mr Nadler said.

Typically, ethics officials make recommendations that justice department employees are expected to follow, but the final decision on whether to recuse over an appearance of a conflict of interest was always Mr Whitaker's to make, according to past and current officials.

As the justice department's top official, Mr Whitaker had been nominally supervising Mr Mueller and was recently notified in advance of a key guilty plea in the case. So far, Mr Whitaker has not received any briefings on the Mueller investigation, but he may at some point, the senior justice department official said.

The back-and-forth inside the department points to the conflicting views and allegiances surrounding its leader during the Trump administration, at a time when the president has publicly attacked federal law enforcement.

Mr Whitaker's rejection of his department's ethics advice is likely to spur renewed criticism from Democrats, who have challenged the legality of Mr Trump's appointment of Mr Whitaker, a justice department staffer who had not been confirmed by the Senate. Mr Trump forced out former attorney general Jeff Sessions on 7 November.

Senator Mark Warner said in a statement that Mr Whitaker's disregarding the opinion of a senior ethics official was "deeply alarming" and "only reinforces the probability that his antagonism towards the Mueller probe was the sole reason for his selection as Acting Attorney General in the first place". Representative Adam Schiff said in a tweet that the justice department's ethics opinion should be shared with Congress, adding, "DOJ officials must avoid not only actual impropriety but the appearance of impropriety."

Before coming to the justice department to serve as Mr Sessions' chief of staff, Mr Whitaker was a TV legal commentator who wrote and spoke frequently about the Mueller probe – almost always in critical ways. He suggested, for example, on CNN that he could envision a scenario where Mr Sessions was replaced and his successor "just reduces [Mueller's] budget to so low that his investigation grinds to almost a halt".

The ethics controversy surrounding Mr Whitaker could also have consequences for his chosen successor, Mr Barr.

Now in private practice, Mr Barr has similarly made public comments that are sceptical of Mr Mueller, and this week, the Senate Judiciary Committee released a memo he sent to the justice department criticising the special counsel for a "fatally misconceived" legal theory of how Mr Trump may have obstructed justice.

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The document, first reported by the Wall Street Journal, is sure to intensify the fight over Mr Barr's confirmation. Senator Dianne Feinstein of California, the Senate Judiciary Committee's top Democrat, said on Thursday the memo was "very troubling" and she would be asking questions about it. Democrats might try to force Mr Barr's recusal as a condition of confirming him, though Republicans will still control the Senate next year.

Two people familiar with the document said Mr Barr made the decision to submit it on his own – not at the direction of the justice department or the White House. Deputy Attorney General Rod Rosenstein said on Thursday that the memo "had no impact on our investigation".

Mr Whitaker's comments were more prolific and blunter. He wrote in a piece for CNN that Mr Trump was "absolutely correct" to suggest Mr Mueller would be crossing a red line by examining the finances of Mr Trump and his family.

Speaking about the June 2016 encounter at Trump Tower – where Jared Kushner, Donald Trump Jr and others met with a Russian lawyer promising dirt on Hillary Clinton – Mr Whitaker said: "To suggest that there's a conspiracy here, I mean, you would always take that meeting."

An audio recording has circulated online in which Mr Whitaker expresses doubt about any Russian interference in American politics.

"The left is trying to sow this theory that essentially Russians interfered with the US election. Which has been proven false. They did not have any impact in the election," he said.

Mr Sessions had been recused from Mr Mueller's probe, which has examined possible coordination between the Trump campaign and the Kremlin, as well as possible obstruction of justice by the president, because Mr Sessions was a part of the Trump campaign. That left Mr Rosenstein, who appointed Mr Mueller, in charge.

But when Mr Trump fired Mr Sessions, Mr Whitaker took command of the Russia investigation. He intimated to associates that he had no intention of recusing himself. Mr Sessions, after all, was fired in part because the president was frustrated he had stepped aside.

Democrats and others expressed alarm about Mr Whitaker's past views, fearful he might stifle Mr Mueller's work. The special counsel regulations call for Mr Whitaker, as acting attorney general, to be notified of significant events in the probe and give him the ability to veto any step he considered "so inappropriate or unwarranted under established departmental practices that it should not be pursued". If he does that, though, he would be required to notify Congress at the end of the case.

Last month, the special counsel's office notified Mr Whitaker in advance that former Trump lawyer Michael Cohen was going to plead guilty to lying to Congress about a possible Trump business project in Moscow.

Asked about his role in the Mueller probe at a news conference on Thursday, Mr Rosenstein said: "We've continued to manage the investigation as we have in the past, and it's being handled appropriately."

Some legal analysts had dismissed Mr Whitaker's public comments about the Mueller probe as essentially uninformed speculation that probably would not force him to step aside. Mr Whitaker did, though, have a relationship with Sam Clovis, a Trump campaign adviser who has testified before the grand jury in Mr Mueller's case.

In 2014, Mr Whitaker chaired the campaign for Mr Clovis when he ran as a Republican candidate for Iowa state treasurer. Mr Clovis told The Washington Post he still considered Mr Whitaker a friend.