Story highlights The dossier explicitly accuses Cohen of being a key link between the Russian government and the Trump campaign

The detailed rebuttal comes as Cohen has emerged as a central figure in the Russia probes

Washington (CNN) The lawyer for a close ally of President Donald Trump fought back against some of the most explosive allegations included in a Russia dossier and argued that congressional investigators should be searching for the donors who paid for it.

In a detailed letter sent to members of the House intelligence committee earlier this month, Stephen Ryan, who represents Michael Cohen, a former Trump Organization executive who is now the President's personal attorney, said the dossier's allegations were unfounded.

The 35-page dossier, compiled by a former British intelligence officer working with a former investigative reporter, explicitly accuses Cohen of being a key link between the Russian government and the Trump campaign -- a charge he has repeatedly and flatly denied.

"We have not uncovered a single document that would in any way corroborate the Dossier's allegations regarding Mr. Cohen, nor do we believe that any such document exists," Ryan wrote to Reps. Michael Conaway and Adam Schiff, the leaders of the House Russia probe, according to a copy of the letter obtained by CNN.

Ryan goes on to say that House investigators should "discern and publicly disclose the entity or entities that paid for the 35-page dossier."

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