Top Democratic lawmakers on Thursday called on Attorney General Jeff Sessions to resign amid reports that he misled a Senate committee about his contacts with Russian officials.

The Washington Post first reported Wednesday evening that Sessions had spoken with Russia’s ambassador to the U.S., Sergey Kislyak, twice last year while also serving in a senior role on President Donald Trump’s campaign.

During his confirmation hearing last month, however, Sessions said he “did not have communications with the Russians.”

House Minority Leader Nancy Pelosi was the first Democrat to call on Sessions to step down, accusing the former Alabama senator of perjuring himself. In a statement released late Wednesday, Pelosi said Sessions is “not fit to serve as the top law-enforcement officer of our country.” Sessions, she said, “lied under oath during his confirmation hearing before the Senate.”

“I remind you this Congress impeached a president for something so far less,” Pelosi added Thursday.

In a statement late Wednesday night, Sessions said, “I have never met with any Russian officials to discuss issues of the campaign. I have no idea what this allegation is about. It is false.” When asked about it on Thursday morning, Sessions reiterated that he did not meet with Russians to “discuss any political campaign.”

Sessions’s spokeswoman, Sarah Isgur Flores, said the attorney general did not mislead the committee because he was not asked about “meetings he took as a senator and a member of the Armed Services Committee.”

The revelation comes as there are growing calls among Democrats and a handful of Republicans for Sessions to appoint an independent special prosecutor to handle the investigation into the Trump campaign’s potential ties with Russia, claiming Sessions cannot act as a neutral arbiter due to his role with the campaign.

Later Thursday, all Democratic members of the House Judiciary Committee sent a letter to FBI Director James Comey and the U.S. Attorney for the District of Columbia, Channing D. Phillips, calling for a criminal investigation into Sessions’ statements “which could potentially implicate a number of criminal laws including lying to Congress and perjury.”

Rep. Elijah Cummings (D-MD), the ranking member of the House Oversight and Government Reform Committee, also called on Sessions to resign, deeming his statements to Congress about Russian communications “demonstrably false.”

Rep. Adam Schiff (D-CA), the top Democrat on the House Intelligence Committee, said it is “essential” that Session recuse himself from any investigation into Trump's relationship with the Kremlin. “This is not even a close call: It is a must,” Schiff tweeted.

Sen. Elizabeth Warren, a progressive stalwart who led the Democratic charge against Sessions’s confirmation, tweeted, “We need Attorney General Jeff Sessions—who should have never been confirmed in the first place—to resign. We need it now.” Kamala Harris, the freshman senator from California whose name is often mentioned as a potential 2020 presidential candidate, joined those calls.

Later Thursday morning, Senate Minority Leader Chuck Schumer (D-NY) also suggested that Sessions step down, adding that the Justice Department should appoint a special prosecutor to look into the Trump campaign’s potential ties with Russia.

Rep. Keith Ellison (D-MN) went a step further, accusing Sessions of perjuring himself and bringing up potential criminal punishment. “We must be entirely clear on one thing: perjury is a felony and may be punishable by prison for up to five years,” he wrote.

Sen. Joe Manchin, a conservative Democrat from West Virginia, told The Daily Beast on Thursday that Sessions should resign if he lied about his contacts with the Russian ambassador. Manchin was the only Democratic senator to vote to confirm Sessions as attorney general.

Reps. Maxine Waters (D-CA) and Betty McCollum (D-MN) joined the chorus of Democrats who characterized the Trump administration as scandal-ridden and untrustworthy.

“Those of us who opposed Sessions from the beginning saw him for who he was—a throwback and a liar,” Waters wrote on Twitter. “Sessions needs to resign, immediately.”

“It is obvious that the Trump administration cannot be trusted to investigate itself,” McCollum said. “It is long past time for Congressional Republicans to put country before party, stop the Trump administration’s cover-up, and get to the bottom of the scandals that have already tarred this presidency.”

Sen. Bernie Sanders, a 2016 Democratic presidential candidate, said Sessions should resign and a special prosecutor should take over the probe in order to “give the American people credible answers about Russia’s involvement in the U.S. election.”

Texas Congresswoman Sheila Jackson Lee tweeted on Thursday: “Recusal is no longer an option. AG Sessions betrayed the trust of the American people and must step down immediately #SessionsLied.”

Virigina Sen. Tim Kaine, the 2016 Democratic vice-presidential nominee, did not go as far as to say that Sessions should resign immediately, but said the attorney general should be questioned by the Senate Judiciary Committee and step down if his answers are not “satisfactory.”

Sen. Dianne Feinstein (D-CA) struck a similar chord, calling the controversy “unacceptable.” She added, “If the attorney general refuses to recuse himself, he should resign.” Feinstein, like others, called for the appointment of a special prosecutor to investigate the extent of the campaign’s communication with Russian officials.