Former Trump adviser George Papadopoulos should spend at least some time in prison for lying to the FBI during the Russia investigation, prosecutors working for special counsel Robert Mueller said in a court filing on Friday.

The filing also revealed several new details about the early days of the investigation.

The prosecutors disclosed that Papadopoulos, a foreign policy adviser to Donald Trump during the 2016 election, caused irreparable damage to the investigation because he lied repeatedly in an interview in January 2017.

Those lies, they said, resulted in the FBI missing an opportunity to properly question a professor Papadopoulos was in contact with who told him Russians possessed “dirt” on Hillary Clinton, in the form of emails.

The filing by the special counsel’s office strongly suggests the FBI had contact with Joseph Mifsud while he was in the US during the early part of the investigation into Russian election interference and possible coordination with Trump associates.

According to prosecutors, the FBI “located” Mifsud in Washington about two weeks after Papadopoulos’ interview and Papadopoulos’ lies “substantially hindered investigators’ ability to effectively question” him. The filing does not relate any details of an interview with the professor.

“The defendant’s lies undermined investigators’ ability to challenge the professor or potentially detain or arrest him while he was still in the United States,” Mueller’s team writes, noting that Mifsud left the US in February 2017 and has not returned.

Prosecutors note that investigators also missed an opportunity to interview others about Mifsud’s comments or anyone else who might have known about Russian efforts to obtain derogatory information on Clinton during the campaign.

“Had the defendant told the FBI the truth when he was interviewed in January 2017, the FBI could have quickly taken numerous investigative steps to help determine, for example, how and where the professor obtained the information, why the professor provided the information to the defendant, and what the defendant did with the information after receiving it,” the court filing says.

Prosecutors also detail a series of interviews with Papadopoulos after he was arrested in July 2017, saying he did not provide “substantial assistance”. As part of a plea deal, Papadopoulos later pleaded guilty to lying to the FBI.

The filing recommends Papadopoulos spend at least some time incarcerated and pay a fine of nearly $10,000. His recommended sentence under federal guidelines is zero to six months, but prosecutors note another defendant in the case spent 30 days in jail for lying to the FBI.

The Russia investigation began as an FBI counter-intelligence operation in July 2016, triggered by information about Papadopoulos. The operation was taken over by Mueller.

Papadopoulos was the first Trump adviser to plead guilty in Mueller’s investigation. Since then, Mueller has returned two sweeping indictments that detail a Russian campaign to undermine the US election, hurt Clinton and help Trump.

Thirteen Russian nationals and three companies are charged with participating in a conspiracy by manipulating social media platforms. Last month, Mueller indicted 12 Russian intelligence operatives, accusing them of hacking the computer systems of Clinton’s presidential campaign and the Democratic party and releasing tens of thousands of private emails through WikiLeaks.

According to that indictment, by April 2016 the Russians had stolen emails from Democratic groups including the Clinton campaign and were beginning to plan how to release the documents.

The same month, according to court papers, Mifsud told Papadopoulos he had met senior Russian government officials in Moscow and learned they had “dirt” on Clinton in the form of “thousands of emails”.