Robert Costello said he told the grand jury Cohen essentially acted alone in paying Stormy Daniels. Cohen disputed that account on MSNBC by saying Costello has his "facts twisted."

The former president is expected to be indicted soon by a grand jury for his role in a hush money payment made to porn star Stormy Daniels on the eve of the 2016 election.

Robert J Costello, scheduled to appear before New York grand jury on Monday, likely to question Trump accuser’s credibility

Michael Cohen waited in vain Monday to be called as the final, rebuttal witness. The grand jury is not expected to meet again until Wednesday.

The indictment of a former president would be a remarkable moment in the country’s history in a case with a legal underpinning that appears far from open-and-shut.

The grand jury is considering a case against the former president over hush money paid to ex-porn actress Stormy Daniels. The case may see criminal charges brought against Mr Trump. Mr Costello has been called by Mr Trump's legal team to discredit previous testimony by Mr Cohen.

Lawyer Robert Costello testified at the request of the Trump legal team and said a key prosecution witness is unreliable.