Washington(CNN) The Justice Department's internal watchdog announced Wednesday it has launched a probe into the department and the FBI's handling of warrant applications under the Foreign Intelligence Surveillance Act.
The review by Inspector General Michael Horowitz came after requests from Attorney General Jeff Sessions and members of Congress, the IG's office said.
For weeks, President Donald Trump and his allies on Capitol Hill have pointed to the House Intelligence Committee's controversial memo -- the so-called Nunes Memo -- slamming how the FBI obtained a FISA warrant to monitor Trump foreign policy aide Carter Page to argue that the nation's top law enforcement agency is politically biased. The memo claims the FBI failed to adequately inform the judge who approved the warrant that it relied, in part, on opposition research funded by the Democratic National Committee and Clinton's campaign.
The IG "will review information that was known to the DOJ and the FBI at the time the applications were filed from or about an alleged FBI confidential source," Horowitz's office said. The investigation will also "review the DOJ's and FBI's relationship and communications with the alleged source as they relate to the (Foreign Intelligence Surveillance Court) applications."
Sessions told reporters last month that Horowitz's office was looking at whether the FBI handled the FISA warrant on Page properly -- prompting Trump to lash out on Twitter and causing Sessions to respond with a rare statement defending his "integrity and honor."
Trump argued that the inspector general was the wrong venue to probe possible FISA and concluded it was "disgraceful."
"Why is A.G. Jeff Sessions asking the Inspector General to investigate potentially massive FISA abuse. Will take forever, has no prosecutorial power and already late with reports on Comey etc," Trump tweeted. "Isn't the I.G. an Obama guy? Why not use Justice Department lawyers? DISGRACEFUL!"
Sessions responded by defending the Justice Department, saying that DOJ "initiated the appropriate process that will ensure complaints against this department will be fully and fairly acted upon if necessary."
But Wednesday's move from the inspector general is also not likely to tamp down the criticism coming from Republicans on Capitol Hill, where there have been numerous calls for Sessions -- or Deputy Attorney General Rod Rosenstein -- to appoint a second special counsel to investigate possible FISA abuse.
House Judiciary Chairman Bob Goodlatte and Oversight Chairman Trey Gowdy said earlier this month they wanted a new special counsel because the scope of the investigation was too broad for the inspector general, arguing the IG could not call relevant witnesses who didn't work at the Justice Department or FBI.
Senate Judiciary Chairman Chuck Grassley, along with Republican Sens. Lindsey Graham of South Carolina, John Cornyn of Texas and Thom Tillis of North Carolina, also called for a second special counsel to investigate the FBI's handling of the Russian investigation and the FISA warrant for Page.
The memo spearheaded by House Intelligence Chairman Devin Nunes accused the FBI of improperly obtaining the FISA warrant by relying on the opposition dossier authored by ex-British intelligence agent Christopher Steele, and hiding the fact he was funded by Democrats and the Clinton campaign. Democrats responded with their own memo saying the FISA warrant was properly obtained, and the FBI made a rare public statement charging that the Nunes memo had "material omissions of fact."
While Horowitz himself does not have prosecutorial powers, he can make criminal referrals to the Justice Department stemming from his investigations.
Horowitz is already working to finish another investigation into the FBI's handling of the Clinton email investigation. Allegations stemming from that probe led to the firing of former FBI Director Andrew McCabe two days shy of his retirement.