A federal judge has thrown out a civil lawsuit by President Donald Trump's former campaign chairman Paul Manafort.

The decision undercuts Manafort's attempt to challenge the special counsel Robert Mueller's authority in the investigation into Russian involvement in the 2016 presidential election.

A federal judge in Washington has thrown out a civil lawsuit brought by President Donald Trump's former campaign chairman that sought to challenge the authority of the special counsel in the Russia investigation.

The decision was a blow to Paul Manafort's defense against special counsel Robert Mueller. U.S. District Judge Amy Berman Jackson issued the ruling.

Manafort's attorneys had initially asked Jackson to throw out all charges against Manafort, arguing that Mueller had exceeded his authority by bringing charges unrelated to Russian election interference.

Their strategy centered around establishing two things: that Rod Rosenstein, the deputy attorney general, gave Mueller an improper and overly broad mandate when he appointed him special counsel in May, and that Mueller overstepped that mandate by charging Manafort with crimes unrelated to Russian collusion.

In particular, Manafort's attorneys pointed to an August memo that Rosenstein sent Mueller as evidence that Rosenstein "got something wrong" when he tapped Mueller to oversee the investigation into Russia's meddling in the 2016 US election and whether the Trump campaign colluded with Russia to influence the outcome.

Almost three months after appointing Mueller, Rosenstein sent a memo to Mueller authorizing him to investigate specific allegations related to Manafort, including but not limited to his Ukraine lobbying work and possible collusion with Russia.

Manafort's main defense lawyer, Kevin Downing, suggested last week that Rosenstein sent the memo because he failed to properly outline the scope of Mueller's mandate at the time of his appointment, as required by Justice Department regulations.

Manafort's lawyers filed motions to suppress evidence the FBI obtained during two searches — one of Manafort's home last July, and another of a storage locker belonging to Manafort's consulting firm last May — arguing that if Mueller's mandate was not properly outlined at the time, the evidence obtained should not be admissible in court.

Jackson hinted last week that the searches could be challenged on those grounds.

Manafort's lawyers dropped the bulk of their challenge in recent weeks, asking Jackson to nullify a paragraph in Mueller's appointment order. They also asked Jackson to issue an order protecting Manafort from future prosecutions by Mueller. The Justice Department had moved for dismissal of the lawsuit.

In Friday’s filing, Jackson said that a civil case was “not the appropriate vehicle” for Manafort’s concerns about “what a prosecutor has done in the past or where he might be headed in the future.”

She added that if Manafort’s concerns would be more appropriately brought in a criminal case.

Read Jackson's full ruling below: