Democratic Representative-elect Alexandria Ocasio-Cortez of New York talks to reporters as she arrives for a class photo with incoming newly elected members of the U.S. House of Representatives on Capitol Hill in Washington, U.S., November 14, 2018.

Rep. Alexandria Ocasio-Cortez is dinging Facebook, Microsoft and Google for "implicit" support of climate change denial in a letter addressed to the CEOs of the three tech companies.

Facebook, Microsoft and Google were "high-level" sponsors of the recent LibertyCon conference in Washington, D.C., which hosted a session "denying established science on climate change," Ocasio-Cortez, D-N.Y., and Rep. Chellie Pingree, D-Maine, said in the joint letter.

"The example you have set promoting sustainability and evidence-based science is compromised by your implicit support of the session organized at LibertyCon," the congresswomen wrote. "Given the magnitude and urgency of the climate crisis that we are now facing, we find it imperative to ensure that the climate-related views espoused at LibertyCon do not reflect the values of your companies going forward."

Ocasio-Cortez and Pingree also note the tech companies have installed sustainable practices in their respective businesses, and concede that conference sponsorship is commonplace. The congresswomen are asking Facebook, Microsoft and Google to reaffirm their commitment to a "more sustainable future."

Ocasio-Cortez and Pingree's letter appear to be in response to a Mother Jones article from last week that noted Google, Facebook and Microsoft were sponsors of the convention earlier this month along with a group called the CO2 Coalition, which denies climate change and attempts to promote the supposed benefits of CO2 emissions.

The three tech companies told Mother Jones in statements last week that they often sponsor events involving technology policy from across the political spectrum.

In a statement to CNBC on Monday, Facebook pointed to a 2017 blog post about the company's political engagement and to the company's sustainability policies.

A spokesperson for Google told CNBC the company sponsors "organizations from across the political spectrum" and that "Google's sponsorship or collaboration with a third party organization doesn't mean that we endorse the organization's entire agenda or agree with other speakers or sponsors."

Microsoft, in a statement, said the company's engagement with LibertyCon was "through a breakfast reception for student leaders to discuss topics including rural broadband and privacy."

"Climate change is one of the most important issues of our time, and our commitment to addressing it is unequivocal. For the past decade, we've reduced emissions, invested in renewable energy, supported policies to address climate change and enabled people around the globe to use technology to accelerate progress on this issue," the company said.

Read the full letter here.

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