The office of former president Barack Obama strongly condemned a Senate committee’s request for records related to Ukraine, dismissing the probe as “without precedent” and a way to “give credence to a Russian disinformation campaign.”

The letter, sent March 13 on official Barack and Michelle Obama letterhead to the National Archives and Records Administration, agreed to release the records “in the interest of countering the misinformation campaign underlying this request,” according to a copy obtained first by BuzzFeed News.

Republican Sens. Ron Johnson (Wis.) and Charles E. Grassley (Iowa) are leading an investigation into Joe Biden, his son Hunter and their engagements with Ukraine. They are also seeking information about interactions between other Democrats and Ukraine related to an unsubstantiated claim that it was Ukraine that interfered in the 2016 election.

The Obama letter, signed by the former president’s records representative, said the probe “arises out of efforts by some, actively supported by Russia, to shift the blame for Russian interference in the 2016 election to Ukraine,” which it noted “has already been thoroughly investigated by a bipartisan congressional committee.”

The letter does not explicitly mention Biden, Obama’s vice president, who Republicans are investigating for conflicts of interest during his time at the White House. Hunter Biden had a lucrative spot on the board of a Ukrainian natural gas company, Burisma, while his father was the Obama administration’s point person on Ukraine policy.

Trump’s impeachment centered on his desire for such an investigation into Hunter Biden and, by extension, Joe Biden, now the presumptive Democratic presidential nominee. The president was charged by the House in December with abuse of power for allegedly withholding military aid to pressure Ukraine to publicly announce an investigation into the Bidens. The Senate voted in February to acquit him.

Johnson, chairman of the Senate Homeland Security and Governmental Affairs Committee, and Grassley, chairman of the Finance Committee, began working on their investigation into Biden and alleged Ukrainian election interference while the House was deep into its impeachment inquiry.

Democrats have slammed the GOP probe as politically motived to hurt Biden before the general election.

Johnson and Grassley sent a joint letter in November to the National Archives requesting all records pertaining to White House meetings “between and among Obama administration officials, Ukrainian government representatives, and Democratic National Committee (DNC) officials.”

In agreeing to allow the senators access to the records, Obama’s office scolded them for “abuse” of the process that gives Congress permission to request access to presidential records before they are publicly available.