Donald Trump accused the FBI of running a "corrupt" investigation into him after it emerged Timothy Thibault, an FBI assistant special agent in charge who was involved with the Hunter Biden laptop investigation, had retired from the bureau.

A security source told Fox News that Thibault, who worked at the FBI's Washington Field Office, was escorted out of the building on Friday as is standard practice when an agent leaves.

Thibault had recently been accused of being "politically biased" by Republican Senator Chuck Grassley, in a letter sent to FBI director Christopher Wray and Attorney General Merrick Garland.