Alexander Vindman's lawyer has hit back at Trump, accusing him of waging a 'campaign of intimidation' against impeachment witnesses

An attorney for Alexander Vindman, the National Security Council official sacked by Trump after testifying in the president's impeachment probe, has accused the president of waging a "campaign of intimidation."

In a statement released after the president launched an attack on Vindman on Twitter the official's attorney, David Pressman, said Trump "made a series of obviously false statements concerning Lieutenant Colonel Vindman."

"They conflict with the clear personnel record and the entirety of the impeachment record of which the president is well aware."

He added: "While the most powerful man in the world continues his campaign of intimidation, while too many entrusted with political office continue to remain silent, Lieutenant Colonel Vindman continues his service to our country as a decorated, active duty member of our military."

Earlier Saturday, Trump had in tweets questioned Vindman's professional record and integrity, having the day before removed him as the top Ukraine expert on the NSC. 

"He was very insubordinate, reported contents of my 'perfect' calls incorrectly, & was given a horrendous report by his superior, the man he reported to, who publicly stated that Vindman had problems with judgement, adhering to the chain of command and leaking information.  In other words, 'OUT'"", tweeted the president. 

Trump's actions have sparked fears among witnesses that there could be further retaliation in store, reported the Washington Post. 

"You look around and you see the adverse actions taken against people who testified under subpoena and it creates a real air of uncertainty," a lawyer for one of the witnesses, who spoke on the condition of anonymity for fear of retribution from the White House, told the publication. 

Vindman, a decorated military officer, in November testified as part of the House's investigation into Trump's campaign to pressure Ukraine to announce a probe into top domestic rival Joe Biden, and his alleged use of withheld military aid as a bargaining chip. 

In his testimony, Vindman had told lawmakers of his concern after hearing Trump's July 25 phone call with President Volodymyr Zelensky of Ukraine, in which Trump had requested a Biden probe as a "favor." 

A whistleblower's complaint about the phonecall sparked the impeachment probe. 

After being acquitted of abusing his office and obstruction the congressional probe last week, Trump has purged Vindman and his brother from the White House, reassigning them back to the Defense Department, and another impeachment witness, EU ambassador Gordon Sondland. 

Sondland had told the impeachment probe that Trump had made a White House visit for Ukraine's President Volodymyr Zelensky conditional on the announcement of a Biden probe.