When he was interviewed by the FBI this January, he falsely claimed that he had met two figures with Russian connections before joining the Trump campaign in March 2016. In fact, he met them after joining the campaign.
One was an unnamed Russian woman who, Mr Papadopoulos believed, had connections to Russian government officials.
He admitted seeking to use her connections in an effort to arrange a meeting “between the Campaign and Russian government officials”.
The other person was an unnamed, London-based professor who was said to have “substantial connections to Russian government officials”.
The professor only took an interest in Mr Papadopoulos because of his status within the Trump campaign, the statement says.
Russian “dirt” on Mrs Clinton, in the form of “thousands of emails”, was allegedly mentioned by the professor at a breakfast meeting in a London hotel on or around 26 April 2016.
The professor said he had been informed about the compromising emails when he met senior Russian government officials on a recent trip to Moscow.
Trump aides have said Mr Papadopoulos played a limited role in the campaign and had no access to Mr Trump, the Associated Press news agency reports.
This may be the real blockbuster
By Anthony Zurcher, BBC News, Washington
Robert Mueller, in journalism terms, buried the story.
Initial headlines on Monday morning were about Paul Manafort’s indictment for money laundering and undisclosed foreign lobbying activities. The real blockbuster, however, may end up being George Papadopoulos’s plea bargain, which was disclosed shortly after the Manafort news came out.
Unlike Mr Manafort, pinched for activities largely conducted before he joined the Trump team, Mr Papadopoulos has admitted to lying to the FBI about contacts he had with Russian nationals while serving as a Trump foreign policy adviser.
Mr Papadopoulos’s indictment document reveals he learned from his connections that Russia claimed to have “dirt” on Democratic candidate Hillary Clinton in the form of “thousands of emails” in a late April 2016 meeting. Damaging emails from the Democratic National Committee and Clinton campaign chair John Podesta started emerging, through Wikileaks, just a few months later.
Now Mr Papadopoulos is co-operating with the independent counsel’s office. At the very least, he has told them who in the top levels of the Trump campaign he was passing this information to.
If Mr Mueller’s case ends up about more than just illegal activities by Mr Manafort and a business associate years ago, Mr Papadopoulos could be a key piece of the puzzle.
What are the charges against Manafort and Gates?
The indictment against the two men, which accuses them of “conspiracy against the United States”, looks at their links to pro-Russian politicians in Ukraine between 2006 and 2015.
It says they acted as “unregistered agents” of Ukrainian politician Viktor Yanukovych and his party, both in opposition and government.