President Donald Trump has said he will "demand" this week that the Justice Department open an investigation into whether the FBI infiltrated his presidential campaign for political purposes.
Mr Trump tweeted: "I hereby demand, and will do so officially tomorrow, that the Department of Justice look into whether or not the FBI/DOJ infiltrated or surveilled the Trump Campaign for Political Purposes - and if any such demands or requests were made by people within the Obama Administration!"
Mr Trump has been promoting a theory circulating in conservative circles about a possible FBI spy on his 2016 campaign, though his attorney has cast doubt on it.
Rudy Giuliani, the attorney representing Mr Trump in the ongoing special counsel's investigation into Russian meddling in the presidential election, said in a television interview last week that neither he nor the president knows for certain if there was a spy on the campaign.
Mr Giuliani said they had been told of "some kind of infiltration".
In any event, the Justice Department's internal watchdog is already examining Republican complaints of FBI misconduct in the early stages of the Russia investigation.
Inspector General Michael E. Horowitz announced an investigation in March at the request of Attorney General Jeff Sessions and congressional Republicans.
Mr Sessions and the lawmakers had urged Mr Horowitz to review whether FBI and Justice Department officials abused their surveillance powers by using information compiled by Christopher Steele, a former British spy, and paid for by Democrats as part of the basis to justify monitoring Carter Page, a former campaign adviser to Mr Trump.
Mr Horowitz said his office will look at those claims as well as communications between Mr Steele and DOJ and FBI officials.
Mr Trump did not elaborate on his "demand," one of a series of tweets he sent throughout the day on Sunday.
On Saturday, Mr Trump tweeted, "If the FBI or DOJ was infiltrating a campaign for the benefit of another campaign, that is a really big deal."
He said only the release or review of documents the House Intelligence Committee is seeking from the Justice Department "can give conclusive answers".
Mr Trump last week accused the Justice Department of trying to frame him by planting a spy in his 2016 campaign.
He quoted Fox Business anchor David Asman and tweeted on Friday: "Apparently the DOJ put a Spy in the Trump Campaign. This has never been done before and by any means necessary, they are out to frame Donald Trump for crimes he didn't commit."
But when asked whether there was an informant on the campaign, Mr Giuliani told CNN: "I don't know for sure, nor does the president, if there really was one," though he said they have long been told there was "some kind of infiltration".