John Dean, a key witness in the Watergate scandal that engulfed former President Richard Nixon, says Donald Trump’s personal attorney has identified the president as a “criminal” and implicated him in a “campaign conspiracy”.

Mr Dean served as White House counsel for Mr Nixon from July 1970 to April 1973, and aided in the cover-up of the Watergate burglaries. He later testified against the president in exchange for a lighter sentence.

The story shares parallels with that of Michael Cohen, Mr Trump’s long-time attorney and personal “fixer,” who pleaded guilty on Tuesday to charges of tax fraud, making false statements to a bank, and campaign finance violations.

Mr Cohen also admitted to having concealed damaging information "in coordination and at the direction of a candidate for federal office”. While he did not identify Mr Trump directly, he was easily identified as the candidate in question.

“He has pretty much identified the president as a criminal. He said he did it at his behest,” Mr Dean told Time after the hearing. “If [Trump] weren’t President, he probably would be named as a co-conspirator and indicted.”

Mr Trump tweeted on Wednesday morning that the campaign finance violations Mr Cohen pleaded guilty to, were "not a crime" and he has denied any conspiracy.

Senator Richard Blumenthal says the US is in a Watergate moment after Michael Cohen pleads guilty

Mr Cohen on Tuesday admitted to paying one woman $130,000 for her silence, and coordinating a payment of $150,000 from American Media Inc to another. Mr Trump has denied having an affair with either woman. Although mr Cohen did not name them, the two women are adult film star Siormy daniels, real name

Mr Dean made a direct comparison on Tuesday between Mr Trump and Mr Cohen’s activities and the infamous Watergate scandal.

“It’s conspiracy,” Mr Dean said of the two men’s dealings. “Watergate was a conspiracy. This is a campaign conspiracy.”

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The comments were echoed by Lanny Davis, an attorney for Mr Cohen, who told CBS News on Wednesday that Mr Trump had “committed a crime” and should be indicted. Mr Dean said he had been in contact with Mr Davis in the run-up to Mr Cohen’s plea, and that the attorney had asked for a refresher on the events in the Watergate case.

Senator Richard Blumenthal, a Democrat on the Senate judiciary committee, told CNN the country was in a "Watergate moment".

"We need bipartisanship now more than ever to protect the special counsel and to stop – and I must underscore stop – any consideration of pardons," Mr Blumenthal said, referring to Robert Mueller, the special counsel whose investigation lead to the charges against Mr Cohen.

Mr Trump did not comment on Mr Cohen’s guilty plea during a campaign rally on Tuesday night, but did express sympathy for his former campaign manager, Paul Manafort, who was convicted that same day on charges of bank fraud and tax evasion.