(TFA), wrote a letter to congressional committees to say Special Counsel Robert Mueller's team had improperly received the emails from the General Services Administration (GSA), a government agency.
But the investigators did not directly request the records from Trump's still-existing transition group, Trump for America, and instead obtained them from the General Services Administration, a separate federal agency that stored the material, according to those familiar with the Trump transition organization.
A spokesman for the Special Counsel's Office declined to comment.
There was no immediate reply Saturday to a request for comment from Mueller's office.
Numerous emails that Mueller's investigators have now include national security discussions about possible Trump worldwide aims as well as candid assessments of candidates for top government posts, said those familiar with the transition. The effort to rein in the probe is expected to increase as the Russian Federation prosecutors continue their work while they simultaneously prepare for a criminal trial next year against former Trump campaign chairman Paul Manafort and his deputy, Rick Gates.
The emails pertain to 13 senior transition officials and many include national security discussions about possible Trump worldwide aims.
"I seriously doubt there is anything here to taint the [Mueller] investigation", said William Jeffress, a white-collar defense attorney who represented Vice President Dick Cheney's senior aide, I. Lewis "Scooter" Libby, during the Valerie Plame CIA leak investigation.
He is said to be cooperating with Mueller's team.
Trump and the White House have repeatedly said that "absolutely no collusion" has taken place nor has been proven by Mueller's investigation.
It's unclear how revelatory the email accounts maintained by the GSA will be for Mueller.
Langhofer wrote in the letter the Special Counsel's Office "was actively using those materials without any notice" to transition officials. It said the special counsel's office has "extensively used the materials in question, including portions that are susceptible to claims of privilege" without notifying the Trump for America team.
Langhofer also said that a GSA official appointed by Trump in May had assured the transition in June that any request for records from Mueller's office would be referred to the transition's attorneys.
The lawyer said the TFA had learned of the disclosure last week. Beckler was "hospitalized and incapacitated" in August and died the following month. GSA career staff, he added, produced the materials without making exceptions for attorney-client, deliberative process or presidential communications privileges.
Ken Nahigian, the Trump transition's executive director and trustee, said in an interview that GSA's decision to share the emails with Mueller's office would have a long-term detrimental effect for future transitions.
A former FBI director, Robert Mueller is leading the investigations into the allegations of Russian meddling in the 2016 U.S. presidential election. Some Republicans have argued that Mueller is biased against Trump and should be fired. Both men have pleaded not guilty and a trial is expected next year.
Flynn pleaded guilty this month to lying to the Federal Bureau of Investigation about his contacts with Russian Federation.
As the Trump transition complaint surfaced Saturday, several Democrats and former Justice officials cautioned that it may be an additional attempt at casting doubt on Mueller's integrity.
It asked for Congress to act immediately "to protect future presidential transitions from having their private records misappropriated by government agencies, particularly in the context of sensitive investigations intersecting with political motives". What are they afraid was found?
Congressman Eric Swalwell, a Democrat from California, questioned how "private documents" can be kept on a government email system.
The letter and accusations have been swiftly discounted by Democrats and other legal experts as an attempt to discredit the Russia-Trump investigation.