Democratic presidential front-runner Hillary ClintonHillary Diane Rodham ClintonWoman behind pro-Trump Facebook page denies being influenced by Russians Trump: CNN, MSNBC 'got scammed' into covering Russian-organized rally Pennsylvania Democrats set to win big with new district map MORE on Wednesday took rival Bernie SandersBernard (Bernie) SandersDems ponder gender politics of 2020 nominee 2020 Dem contenders travel to key primary states After Florida school shooting, vows for change but no clear path forward MORE to task for listing Planned Parenthood among the “political establishment” opposed to his campaign.

Sanders said several organizations that have backed Clinton’s candidacy, including Planned Parenthood and the Human Rights Campaign, represent the entrenched political class that he is fighting.

“What we are doing in this campaign — and it just blows my mind every day, because I see it clearly — we’re taking on the political establishment,” Sanders said late Tuesday on MSNBC’s “The Rachel Maddow Show.”

“And so I have friends and supporters in the Human Rights [Campaign], in Planned Parenthood,” he added. “But you know what? Hillary Clinton has been around there for a very, very long time, and some of these groups are, in fact, part of the establishment.”

Clinton was incredulous at the characterization of the abortion rights group.

“Really Senator Sanders?” she tweeted early Wednesday morning. “How can you say that groups like [Planned Parenthood] and [the Human Rights Campaign] are part of the ‘establishment’ you’re taking on?”

Dawn Laguens, executive vice president of Planned Parenthood Action Fund, called Sanders's comments "regrettable."

"I’m disappointed in Senator Sanders’ remarks last night," Laguens said in a statement to The Hill. "This country sees attacks against reproductive health, reproductive rights, and marriage equality every day — especially from every single GOP candidate for President."

"It's regrettable, and surprising, to hear Senator Sanders describe the very groups that fight on behalf of millions of often marginalized Americans — people who still have to fight for their most basic rights — as representing the 'establishment.'  Reproductive health care and rights, and the full equality of LGBTQ people, are core progressive values that should unite us all," she added.

The Human Rights Campaign also weighed in on the exchange, saying they were disappointed by Sanders’s comments.

“We share [Planned Parenthood’s] disappointment in Sanders’ attack,” the Human Rights Campaign tweeted Wednesday morning. "[The Human Rights Campaign] has proudly taken on the establishment & fought for LGBT people for over 30 years.”

The clash over Planned Parenthood comes amid an increasingly competitive Democratic primary race.

In polls, Sanders has closed the gap in the first-in-the-nation Iowa caucuses less than two weeks before ballots are cast, and a new poll shows the Vermont senator leading Clinton by 27 points in the New Hampshire primary.