"The indictment in this case arises from multiple glaring constitutional violations and an egregious abuse of power by the federal government," Comey's legal team wrote in one of two filings, which said the case should be dismissed on the basis of it being a vindictive and selective prosecution.
"President Trump ordered the Department of Justice (DOJ) to prosecute Mr Comey because of personal spite and because Mr Comey has frequently criticised the president for his conduct in office," his lawyers said.
Comey was the first of three of Trump's political foes to be criminally charged in recent weeks. Since then, the Justice Department has also brought charges against New York State Attorney General Letitia James, who filed a civil fraud lawsuit against Trump while he was out of power, and Trump's former National Security Adviser John Bolton, who has publicly said Trump is unfit to be president.
Comey pleaded not guilty to charges of making false statements and obstructing a congressional investigation, which were brought by Trump's former personal lawyer, Lindsey Halligan. Halligan was installed  as the top federal prosecutor in the Eastern District of Virginia after Trump forced out her predecessor over his reticence to prosecute Comey and James.
The indictment accuses Comey of authorising an FBI employee to disclose information about a federal probe. The indictment does not identify the investigation, but it appears to relate to Hillary Clinton, Trump's rival in the 2016 presidential race.
In a second court filing on Monday, Comey's lawyers said Trump violated the law when he installed Halligan as interim US lawyer. Since she is the only person who signed the indictment, the case is not valid, they said.
"The official who purported to secure and sign the indictment was invalidly appointed to her position as interim US Attorney. Because of that fundamental constitutional and statutory defect, the indictment is a nullity and must be dismissed," they wrote.
Comey's case is being heard by US District Judge Michael Nachmanoff in Alexandria, Virginia, who has set a January trial date. Nachmanoff has already said the motion arguing that Halligan's appointment was invalid will be decided by a judge in another jurisdiction.
The federal judiciary in Virginia played a role in appointing Halligan's predecessor, and reassigning the motion will avoid the appearance of a conflict of interest, Nachmanoff said.
