Wilmer Cutler Pickering Hale and Dorr partner Robert Mueller, the former director of the FBI, is leaving his perch in private practice to take on the high profile and politically precarious role as special counsel investigating Russia's efforts to influence the 2016 US presidential election.

Two other WilmerHale partners, Aaron Zebley and James Quarles, have also left the firm, which expects them to join Mueller in the investigation, a WilmerHale spokesperson said.

Deputy attorney general Rod Rosenstein appointed Mueller on Wednesday "to ensure a full and thorough investigation of the Russian government's efforts to interfere in the 2016 presidential election".

The investigation will examine any links between individuals on US President Donald Trump's campaign and the Russian government. Mueller will have the authority to prosecute if needed.

"I accept this responsibility and will discharge it to the best of my ability," Mueller said in a statement provided to Legal Week sister title the National Law Journal.

Trump said he looks forward to the investigation concluding quickly.

"As I have stated many times, a thorough investigation will confirm what we already know – there was no collusion between my campaign and any foreign entity," Trump said in a written statement.

Mueller agreed to resign from WilmerHale to avoid any conflicts of interest. He is followed in leaving the firm by Zebley, his former FBI chief of staff, and litigator Quarles, the former Washington DC head of legacy firm Hale and Dorr, who also worked as an assistant special prosecutor for the Watergate investigation.

All three lawyers' professional biographies were removed from the firm's website on Wednesday.

Widely respected as one of the longest-serving directors of the FBI, Mueller left the department in 2013 and joined WilmerHale the following year.

In private practice, Mueller worked on a range of issues including cybersecurity, criminal litigation and internal investigations. Last year, he was appointed to oversee settlement negotiations in class-action lawsuits over Volkswagen's emissions scandal.

Several Democratic political figures, including Senator Bernie Sanders and former Attorney General Eric Holder, voiced their support for Mueller, while the American Civil Liberties Union, which in November pledged itself in opposition to Trump, issued this statement:

"We welcome the appointment of a special counsel to investigate Russia's meddling in our elections, a critically necessary step given the conflicts of interest present at the Trump administration's highest levels."

Since April, Mueller has been in charge of the distribution of almost $1bn to victims and automakers affected by Takata's defective airbags. He also served as the NFL's independent investigator into the league's handling of a violent episode involving former Baltimore Ravens player Ray Rice.

At the time of that appointment, in 2014, Andrew Weissmann, a former FBI general counsel who worked for Mueller, said, "You're not going to hire Robert Mueller if you're looking for a whitewash."

Indeed, few lawyers and government-focused law firms have built resumes as impressive as Mueller and WilmerHale when it comes to working for Democrats, Republicans and as independent counsel.

Mueller ran the FBI for for more than a decade. President George W Bush appointed him in 2001, a week before the 9/11 attacks. Though FBI directors have a 10-year tenure, President Barack Obama asked Congress to allow him to stay on another two years.

In recent years, WilmerHale has stocked up on former high-ranking US government officials such as Mueller for its ranks, including former Obama-era Deputy Attorney General David Ogden and a Bush-era ambassador to Germany, Robert Kimmitt.

Partner Reginald Brown, who worked in the Bush White House and runs the firm's financial institutions group and congressional investigations practice, is advising Paul Manafort as of this spring. Manafort, who ran Trump's presidential campaign for six months, may be ensnared in the Russia investigation because of a consulting client he represented in Ukraine who had ties to the Kremlin.

Top Clinton administration alumni at WilmerHale include former Solicitor General Seth Waxman and former Deputy Attorney General Jamie Gorelick, who has boosted her own resume in recent months by advising Ivanka Trump and Jared Kushner on government ethics.

In another connection, Hale and Dorr, the predecessor firm, once housed James St Clair, the lawyer who represented Richard Nixon during Watergate. Hale and Dorr merged with Wilmer Cutler Pickering in 2004.

National Law Journal reporter Marcia Coyle contributed to this report.