The US Justice Department is attempting to prosecute former FBI Director James Comey for a third time, the ​latest case accusing him of sharing sensitive national security information in ‌2016, according to court documents made public on Monday.

The case was revealed in a court document known as a “criminal information” that the Justice Department said it filed to stop the 10-year ​statute of limitations on the offence from expiring earlier this month.

The document ​filed in Washington federal court charges Comey with transmitting and conspiring ⁠to transmit national defence information. It alleges he shared classified information with a ​reporter from the New York Times in October 2016.

Comey said in a video on ​Instagram that “they’re back again” and referenced the Justice Department, but did not provide further details. “I’m still innocent,” he added. Comey’s lawyers have already asked a judge to dismiss the case, arguing ​it is legally improper.

“I think he’s a dirty cop,” President Donald Trump told reporters ​at Joint Base Andrews, Maryland, when asked about Comey. “I don’t know much about it,” he said.

The ‌new ⁠case adds to the legal fights facing Comey, whom the Justice Department has already charged twice, accusing him of lying to Congress about media leaks and threatening Trump in a social media post. A judge dismissed the false statements case, while ​the threats case remains ​pending.

Comey’s lawyer, Patrick ⁠Fitzgerald, said in a statement that the document “purports to charge Mr Comey with crimes that he did not commit”. The ​criminal information was filed on October 5, but was unsealed ​on Monday ⁠at the request of Comey’s lawyers.

A Justice Department spokesperson described the manoeuvre to halt the statute of limitations as a “widely recognised practice in federal court”.

“This is an ongoing ⁠criminal investigation, ​and we will not comment further,” the spokesperson ​said in a statement.