The office of former President Barack Obama in March privately bashed Senate Republicans’ investigation of former Vice President Joe Biden and his son in Ukraine, a probe it deemed as lending credence to a “Russian disinformation campaign,” according to a letter obtained by Fox News.

The letter, addressed to the National Archives and Records Administration (NARA), which manages presidential records, was written in response to a request on Nov. 21, 2019, by Republican Sens. Chuck Grassley and Ron Johnson for Obama administration records on Ukraine-related meetings.

FILE: Former President Barack Obama speaking at the Gathering of Rising Leaders in the Asia Pacific, organized by the Obama Foundation in Kuala Lumpur, Malaysia.  (AP)

The letter referred to their request as improper use of the NARA’s release terms and a supposed effort “to shift the blame for Russian interference in the 2016 election to Ukraine.”

It goes on to cite testimony from former National Security aide Fiona Hill who derided the idea of Ukrainian interference in the 2016 election as a “fictional narrative that is being perpetrated and propagated by the Russian security services.”

Under the Presidential Records Act, incumbent and former presidents may claim executive privilege over record requests. However, the NARA is permitted to provide special access to both Houses of Congress ahead of the documents’ scheduled release date.

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The letter, which was first reported by BuzzFeed News, stated that the office of former President Obama has “produced 12,880 pages of presidential records in response to special access requests from the White House and Congress.”

“This use of the special access process serves no legitimate purpose, and does not outweigh or justify infringing confidentiality interests that all presidents have sought to protect,” the letter read.

It continued to say the office permitted Grassley and Johnson’s request “in the interest of countering the misinformation campaign underlying this request.”

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The letter's release comes after Grassley and Johnson, who chair the Senate Finance Committee and the Senate Homeland Security and Governmental Affairs Committee, respectively, sent a letter to the secretary of state last month demanding more information on the Obama administration’s dealings in Ukraine.