The US Justice Department has announced plans to investigate the FBI over its handling of the probe into Hillary Clinton's use of a private email server in her role as secretary of state.

The investigation was announced by Inspector General Michael E Horowitz and will look into allegations FBI director James Comey did not follow department protocol in disclosing information about the probe.

A news release from Horowitz suggested the investigation would look at Comey's letters and information about whether non-public information was leaked by the FBI, The Washington Post reported.

The press release said: "The review will not substitute the OIG's [Office of the Inspector General] judgment for the judgments made by the FBI or the Department regarding the substantive merits of investigative or prosecutive decisions."

The announcement comes following months of criticism over Comey's handling of the email probe – in particular his decision to inform members of congress on 28 November that the email probe, which had previously been closed, was being looked into once again.

Clinton's former campaign spokesman Brian Fallon told the Post: "This is highly encouraging and to be expected given Director Comey's drastic deviation from Justice Department protocol.

"A probe of this sort, however long it takes to conduct, is utterly necessary in order to take the first step to restore the FBI's reputation as a non-partisan institution."

Clinton herself has reportedly blamed Comey for her election defeat, with her supporters citing the timing of his letter to members of congress – less than two weeks before the election, as a particular setback.

Speaking in a call with her campaign funders on 12 November, Clinton said the decision to re-open the investigation into her use of a private email server had been a turning point in the polls, two of the people on the call told Reuters.

After the investigation was announced, Comey said in a statement: "I am grateful to the Department of Justice's IG for taking on this review.

"He is professional and independent and the FBI will cooperate fully with him and his office. I hope very much he is able to share his conclusions and observations with the public because everyone will benefit from thoughtful evaluation and transparency regarding this matter."