Sen. Elizabeth Warren Elizabeth WarrenDimon: Wealth tax 'almost impossible to do' CNN's Don Lemon: 'Blow up the entire system' remark taken out of context Democrats shoot down talk of expanding Supreme Court MORE (D-Mass.) took a swipe at fellow 2020 presidential candidate former Vice President Joe Biden Joe BidenBiden on Trump's refusal to commit to peaceful transfer of power: 'What country are we in?' Democratic groups using Bloomberg money to launch M in Spanish language ads in Florida Harris faces pivotal moment with Supreme Court battle MORE on Friday over a “swanky private fundraiser” he attended following the announcement of his candidacy.

Warren's comments came in a fundraising email sent to supporters asking for donations after Biden announced a staggering $6.3 million fundraising haul within the first 24 hours of launching his campaign.

Warren, who has eschewed donations from corporate PACs and lobbyists, highlighted a fundraiser Biden attended that was hosted by Comcast executive David Cohen and health insurance executive Daniel Hilferty.

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“In the first 24 hours of his presidential campaign (welcome to the race!), Joe Biden raised $6.3 million,” Warren wrote. “How did Joe Biden raise so much money in one day? Well, it helps that he hosted a swanky private fundraiser for wealthy donors at the home of the guy who runs Comcast's lobbying shop.”

“Elizabeth is building a grassroots movement without holding any big-money private fundraisers where you can only talk to her if you write a big check first. Without taking a dime from federally registered lobbyists or PACs of any kind. It’s the right thing to do," she added.

The Wall Street Journal reported Friday that, of the $6.3 million Biden raised in his first 24 hours as a candidate, about $700,000 came from Thursday's fundraiser in Philadelphia, according to organizers.

Warren, a progressive, has made a career out of hammering Wall Street and other financial titans. The 2020 contender also hit Biden Thursday over his 2005 vote for the Bankruptcy Abuse Prevention and Consumer Protection Act, which critics have said empowered credit card companies to target people seeking protection from bankruptcy.

“At a time when the biggest financial institutions in this country were trying to put the squeeze on millions of hardworking families,” she said Thursday, “Joe Biden was on the side of the credit card companies.”

Warren, who was among the earliest to declare her presidential ambitions, has lagged behind other candidates, including Sen. Bernie Sanders Bernie SandersOutrage erupts over Breonna Taylor grand jury ruling Dimon: Wealth tax 'almost impossible to do' Grand jury charges no officers in Breonna Taylor death MORE (I-Vt.) and Biden in fundraising and in polls.

Other candidates have also sworn off donations from lobbyists or PACs, including South Bend, Ind., Mayor Pete Buttigieg Pete ButtigiegThe Hill's Morning Report - Sponsored by Facebook - GOP closes ranks to fill SCOTUS vacancy by November Buttigieg stands in as Pence for Harris's debate practice Hillicon Valley: FBI, DHS warn that foreign hackers will likely spread disinformation around election results | Social media platforms put muscle into National Voter Registration Day | Trump to meet with Republican state officials on tech liability shield MORE, Sanders and Sens. Kamala Harris Kamala HarrisHarris faces pivotal moment with Supreme Court battle Nearly 40 Democratic senators call for climate change questions in debates Joe Biden has long forgotten North Carolina: Today's visit is too late MORE (D-Calif.) and Cory Booker Cory Anthony BookerBipartisan praise pours in after Ginsburg's death DHS opens probe into allegations at Georgia ICE facility Democratic lawmakers call for an investigation into allegations of medical neglect at Georgia ICE facility MORE (D-N.J.)