WASHINGTON (Reuters) - The former British spy who produced a dossier describing alleged links between Donald Trump and Russia will not cooperate with a prosecutor assigned by U.S. Attorney General William Barr to review how the investigations of Trump and his 2016 election campaign began, a source with knowledge of the situation said.

Christopher Steele, a former Russia expert for the British spy agency MI6, will not answer questions from prosecutor John Durham, named by Barr to examine the origins of the investigations into Trump and his campaign team, said the source close to Steele’s London-based private investigation firm, Orbis Business Intelligence.

Trump has given Barr broad authority to declassify intelligence materials related to the investigations. Last week Trump ordered the heads of U.S. spy and law enforcement agencies to cooperate with Durham.

Steele, who had previously collaborated with the FBI on issues such as corruption in the global soccer organization FIFA, was hired in 2016 by Fusion GPS, a Washington-based private investigations firm working for lawyers representing the Democratic Party and Hillary Clinton’s presidential campaign.

Steele produced for Fusion GPS a set of controversial and sometimes salacious reports describing alleged contacts Trump and his team had with Russians before the election.

Trump says Steele’s “fake dossier” was a key factor behind the investigations and what he claims is a broader “witch hunt” against him. He also accuses senior intelligence officials of improperly “spying” on his campaign.

According to documents declassified by the Trump administration, the FBI cited Steele’s reporting as partial justification for electronic surveillance targeting Carter Page, a one-time Trump campaign advisor with business dealings in Russia.

Democrats accuse Trump of trying to turn attention away from the findings of Special Counsel Robert Mueller, whose report into Russian interference in the 2016 election described numerous links between the Trump campaign and Moscow, and said Trump had repeatedly tried to impede the investigation.

The source close to Steele’s company said Steele would not cooperate with Durham’s probe but might cooperate with a parallel inquiry by the Justice Department’s Inspector General into how U.S. law enforcement agencies handled pre-election investigations into both Trump and Clinton.

Steele also cooperated with Mueller’s investigative team, voluntarily submitting to two interviews in September 2017. He also gave written testimony to the U.S. Senate Intelligence Committee in August 2018, the source said.

The Justice Department had no immediate comment, and a spokesman for Durham declined to comment.