The US justice department has expanded a probe into whether the FBI acted with political bias when investigating the Trump campaign’s ties with Russia after pressure from the president.
The department said its inspector general had been tasked with “determining whether there was any impropriety or political motivation” in how the FBI acted before the 2016 vote.
Just hours before the statement was released Donald Trump had tweeted that he would “officially” demand an investigation on Monday.
He questioned whether his predecessor Barack Obama’s administration was involved in the decision to investigation before the election.
Mr Trump’s comment had piled pressure on the Justice Department, whose most senior figures he has repeatedly criticised in public.
The officials are overseeing the Russian election meddling investigation, now being run by special counsel Robert Mueller, that has blighted his presidency.
Republicans have increased focused on how the FBI began invetigating Trump campaign officials’ ties to Russia before the 2016 presidential election.
The FBI had a Foreign Intelligence Surveillance Act [FISA] application approved to put Carter Page, a Trump campaign foreign policy adviser, under surveillance before the vote.
The FBI also reportedly tasked a US academic and informant to approach Mr Page and another Trump campaign official, George Papadopoulos, before the election to work out their ties to Russia.
Mr Trump expresses his fury last week. He tweeted that “word seems to be coming out that the Obama FBI “SPIED ON THE TRUMP CAMPAIGN WITH AN EMBEDDED INFORMANT”, adding: “If so, this is bigger than Watergate!”
He then tweeted on Sunday: “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!”
Within hours, the Justice Department had commented, saying the inspector general - which investigates complaints or allegations of wrongdoing or misconduct by relevant government employees - would look into the claims.
A Justice Department spokesman said: "The Department has asked the Inspector General to expand the ongoing review of the FISA application process to include determining whether there was any impropriety or political motivation in how the FBI conducted its counterintelligence investigation of persons suspected of involvement with the Russian agents who interfered in the 2016 presidential election.”
Rod Rosenstein, the deputy attorney general, said: “If anyone did infiltrate or surveil participants in a presidential campaign for inappropriate purposes, we need to know about it and take appropriate action.”
The moves from the Justice Department appeared to be an attempt to head off Mr Trump’s criticism and calls for a full probe into the matter.
It is unclear whether the announcement will placate the president, given he has criticised using the inspector general in the past because the office lacks prosecutorial power.
There was speculation from US media commentators that Mr Trump’s demand was an attempt to force senior justice officials into resigning.
Jeff Sessions, the US attorney general, and Mr Rosenstein, his deputy, have both been figures of Mr Trump’s public anger in the past.
Mr Sessions recused himself of the Russian election meddling investigation, meaning he cannot shape its course, while Mr Rosenstein is overseeing the probe.
In a separate development, Rudolph Giuliani, Mr Trump’s lawyer, said Robert Mueller, the special counsel now leading the investigation, wanted to end the part looking into obstruction of justice by September 1.
The revelation of the timeframe comes with Mr Mueller seeking to interview Mr Trump about claims he obstructed justice. The allegations have always been denied by the White House.