WASHINGTON (WASHINGTON POST) - The prosecutor handpicked by Attorney-General William Barr to scrutinise how US agencies investigated President Donald Trump's 2016 campaign said he could not offer evidence to the Justice Department's inspector-general to support the suspicions of some conservatives that the case was a set-up by American intelligence, people familiar with the matter said.

Justice Department Inspector-General Michael Horowitz's office contacted US Attorney John Durham, the prosecutor Mr Barr personally tapped to lead a separate review of the 2016 probe into possible coordination between the Trump campaign and Russia, the people said.

The inspector-general also contacted several US intelligence agencies.

Among Mr Horowitz's questions: Whether a Maltese professor who interacted with a Trump campaign adviser was actually a US intelligence asset deployed to ensnare the campaign, the people said, speaking on the condition of anonymity because the inspector-general's findings have not been made public.

But the intelligence agencies said the professor was not among their assets, the people said. And Mr Durham informed Mr Horowitz's office that his investigation had not produced any evidence that might contradict the inspector-general's findings on that point.

Representatives for the inspector-general's office, Mr Durham and the Justice Department all declined to comment.

The previously unreported interaction is noted in a draft of Mr Horowitz's forthcoming report on the Russia investigation, which concludes that the FBI had adequate cause to launch its Russia investigation, people familiar with the matter said. Its public release is set for next Monday (Dec 9).

That could rebut conservatives' doubts - which Mr Barr has shared with associates in recent weeks - that Mr Horowitz might be blessing the FBI's Russia investigation prematurely, and that Mr Durham could potentially find more, particularly with regard to the Maltese professor.

The draft, though, is not final. The inspector-general has yet to release any conclusions, and The Washington Post has not reviewed Mr Horowitz's entire report, even in draft form.

It is also unclear whether Mr Durham has shared the entirety of his findings and evidence with the inspector-general, or merely answered a specific question.

Mr Trump and his allies have relentlessly criticised the FBI probe, which was taken over by special counsel Robert Mueller, as a "witch hunt" and pushed for investigations of those who launched it.

They have been eagerly anticipating the release of Mr Horowitz's report in hopes the watchdog with a non-partisan reputation might validate their attacks.

Mr Barr told CBS News in May that some of the facts he had learned about the Russia case "don't hang together with the official explanations of what happened".

He declined to be more specific.

In response to recent reports about Mr Barr's scepticism about the forthcoming inspector-general report, Justice Department spokesman Kerri Kupec said in a statement that the watchdog's investigation "is a credit to the Department of Justice".

"His excellent work has uncovered significant information that the American people will soon be able to read for themselves," Ms Kupec said.

"Rather than speculating, people should read the report for themselves next week, watch the Inspector-General's testimony before the Senate Judiciary Committee, and draw their own conclusions about these important matters."

Mr Horowitz's draft report concludes that political bias did not taint how top FBI officials running the investigation handled the case, people familiar with the matter said.

But it details troubling misconduct that Mr Trump and his allies are likely to emphasise as they criticise the bureau.

In particular, Mr Horowitz's team found omissions in the FBI's applications to renew warrants from the Foreign Intelligence Surveillance Court to monitor former Trump campaign adviser Carter Page, people familiar with the matter said.

The applications relied at least in part on information provided by Mr Christopher Steele, a former British intelligence officer who was hired to investigate Mr Trump by an opposition research firm working for Mrs Hillary Clinton's presidential campaign.

Relying on a network of sources and sub-sources, Mr Steele claimed he had information on connections between the Trump campaign and the Russian government. He passed that information to the FBI.

When FBI agents interviewed one of Mr Steele's sub-sources, they found that Mr Steele's information - which he had said was raw intelligence in need of further investigation - was not entirely reliable, people familiar with the matter said.

And Mr Horowitz determined in the draft of his report that the FBI failed to convey as much in some of the later applications to surveil Mr Page, the people said.

Those omissions, while significant, were apparently not so egregious as to convince Mr Horowitz to conclude that the renewal applications should have been rejected.

It would be unusual for the inspector-general to sit in judgment over the Foreign Intelligence Surveillance Court's determinations, because his job is to review how the information was gathered and presented to the court, not whether the FISA court should have approved or rejected specific applications.

Mr Horowitz also found that a low-level FBI lawyer, Mr Kevin Clinesmith, doctored an e-mail that was used as part of the warrant application process - potentially significant misconduct that Mr Durham is now exploring as a possible crime, people familiar with the matter said.

Mr Clinesmith, who has not responded to inquiries about the inspector-general's findings, is a familiar name to Republicans critical of the FBI; in a previous report on the FBI's investigation into Mrs Clinton's use of a private e-mail server while she was secretary of state, Mr Horowitz found that the lawyer sent messages suggesting a dislike of Mr Trump, including one saying "Viva le resistance".

When questioned by the inspector-general about such messages, Mr Clinesmith insisted that many of them were jokes and that he did not let his political views affect his work.

A draft of his report criticises as careless another low-level FBI agent who had some involvement in the Russia probe, the people said, though the exact reasons for that remain unclear.

Mr Horowitz's report addresses in detail the cause - referred to in law enforcement circles as "predication" - for opening the Russia investigation.

The bureau did so after the Australian government passed to the US a tip that George Papadopoulos, a Trump campaign aide, had boasted about Russia having political dirt on Mrs Clinton.

The boasts came before it was publicly known that the Kremlin had hacked Democratic e-mails and stolen information that might be damaging to Mrs Clinton's campaign.

Papadopoulos had been told of the possible dirt by Professor Joseph Mifsud, the mysterious Maltese professor.

US officials have long insisted that they were duty bound to follow-up on what seemed to be an alarming tip.

The standard for opening an investigation is low. FBI officials need only an "articulable factual basis" to believe there has been possible criminal activity or a threat to national security.

US officials suspect that Prof Mifsud has ties to Russian intelligence.

Papadopoulos, who pleaded guilty to lying to the FBI about his interactions with Prof Mifsud, has alleged, though, that he believes Prof Mifsud is some type of Western intelligence asset, and that he was set up.

People familiar with the matter said Mr Horowitz queried US intelligence agencies to determine whether there was any truth to that claim, and found no evidence Prof Mifsud was a US asset.

He also reached out to Mr Durham to see whether the prosecutor had found anything that might contradict that assessment, and Mr Durham said he had no such evidence, people familiar with the matter said.

Mr Barr has seemed in recent months to take a keen interest in Prof Mifsud, a shadowy figure who last surfaced two years ago for an interview with a reporter in Italy.

The attorney-general has had private meetings with foreign intelligence officials to ask for their assistance in the Durham investigation, and he has asked the Italian government, in particular, about its knowledge of the professor.

Italian officials told him they had no involvement in the matter.

It was not immediately clear whether Mr Horowitz has examined possible ties between Prof Mifsud and other Western governments outside the US, though people familiar with the draft of his report said it does not lend any credence to Papadopoulos's allegation about the professor.

Mr Barr could formally object to any of Mr Horowitz's assertions - though he could not order the independent watchdog to change anything - as the draft of the inspector-general's report is still being finalised.

In recent weeks, witnesses have given Mr Horowitz input on changes they feel are necessary.

The Justice Department typically offers a written response and sometimes objects to the conclusions of its inspector-general - though generally that occurs when the watchdog is alleging misconduct and the department feels it has to defend itself, rather than when the inspector-general plans to clear the department or the FBI of wrongdoing.

Mr Barr also could decline to formally weigh in, but publicly air his scepticism later, perhaps in a media interview.