Donald Trump's personal lawyer says the president "never, in form or substance" directed former FBI director James Comey to stop investigating anyone.

That includes former national security adviser, Michael Flynn.

Marc Kasowitz is responding to Mr Comey's Thursday morning testimony, in which the fired FBI director said President Trump urged him to drop the Flynn case.

Mr Kasowitz says that the president is "entitled to expect loyalty" from those serving the administration.

But he says President Trump never told Mr Comey: "I need loyalty, I expect loyalty," in form or substance, as Mr Comey claimed.

President Trump tasked Mr Kasowitz late last month with responding to matters arising from various probes of Russian interference in the election.

Mr Kasowitzalso accused Mr Comey of "unauthorised disclosures" of "privileged communications" he had with the president.

He said there continues "to be those in government who are actively attempting to undermine this administration with selective and illegal leaks of classified information and privileged communications".

He added: "Comey has now admitted that he is one of the leakers."

Mr Comey said in his testimony that he leaked his memos of his conversations with the president to a friend after a tweet by the president suggested he may have taped the conversations.

Mr Kasowitz says President Trump's team will "leave it the appropriate authorities" to determine whether the leak should be investigated.