Kash Patel, a one-time aide to President Donald Trump, has been confirmed by the US Senate to lead the Federal Bureau of Investigation (FBI).

Patel, a former defence department chief of staff and ex-federal prosecutor, is a staunch Trump supporter and a fellow critic of the US government’s top law enforcement agency.

He was confirmed in a party line vote of 51-49, with only two Republicans joining all Democrats against him, citing concerns over his qualifications to lead the agency and claiming that he will pursue retribution against critics of Trump.

Patel has previously suggested dramatically limiting the authority of the FBI, which Republicans allege has unfairly targeted conservatives in recent years.

The FBI’s outgoing director Christopher Wray has denied such allegations.

Patel replaces Christopher Wray whom Trump picked in 2017. Wray resigned before inauguration day last month after the incoming Republican president indicated he would fire him.

The FBI director leads 37,000 employees across 55 US field offices. They also oversee 350 satellite offices and more than 60 other foreign locations expected to cover almost 200 countries.

Patel only narrowly cleared the final hurdle, reflecting the deep divisions over his nomination – the last three FBI picks were approved by at least 90 senators.

In his confirmation hearings, Patel denied keeping a list of “deep state” enemies, while playing down controversial past remarks he had made, such as referring to law enforcement officials who investigated Trump as “criminal gangsters”.

The 60-name roster includes former President Joe Biden, former Attorney General Merrick Garland and former National Security Adviser John Bolton, among others.

In his memoir Government Gangsters, published in 2023, Patel called for an eradication of what he called “government tyranny” within the FBI by firing “the top ranks”.

Many conservatives believe a “deep state”, or unelected bureaucratic cabal, is working to thwart Trump’s agenda.

Attorney General Pam Bondi, who is now Patel’s boss, told lawmakers during her confirmation hearing earlier this month that there would be no enemies list at the Department of Justice under her leadership.

Patel, the son of Indian immigrants, is a former defence lawyer and federal prosecutor.

He caught the attention of Trump – who was then serving his first term as president – after becoming a senior counsel to the House of Representatives intelligence committee in 2017.

He quickly rose within Trump’s circle after he was hired as a national security aide in 2019, and in 2020 was appointed chief of staff to the head of the Pentagon.

As well as his 2023 memoir, Patel has published two pro-Trump children’s books.

He is on the board of Trump Media and Technology Group, which owns Trump’s social media platform, Truth Social. He has also reportedly had a consulting contract with the company.

After announcing Patel as his FBI pick, Trump posted on social media calling him “an advocate for truth, accountability, and the constitution”.

“Kash is a brilliant lawyer, investigator, and ‘America First’ fighter who has spent his career exposing corruption, defending justice, and protecting the American people,” Trump said.