Congresswomen Alexandria Ocasio-Cortez and Chellie Pingree addressed a letter to the CEOs of Facebook, Microsoft, and Google Monday after reports showed the tech giants sponsored an event amplifying the benefits of greenhouse gases.

The companies were high-level sponsors of the student libertarian conference LibertyCon in Washington DC last week, which featured a talk promoting climate change denial.

Conference sponsorship is a common practice among tech companies, though the congresswomen hope to have Google, Facebook, and Microsoft reaffirm their commitment to tackling climate change publicly.

Democratic Rep. Alexandria Ocasio-Cortez and Rep. Chellie Pingree sent a letter to the CEOs of Facebook, Microsoft, and Google for sponsoring a libertarian student conference, LibertyCon, which featured a session denying climate change.

The conference, held in Washington DC last week, featured a talk titled “Let’s Talk About Not Talking: Should There Be ‘No Debate’ that Industrial Carbon Dioxide is Causing Climate Catastrophe?” according to Mother Jones. The publication also reported brochures being handed out on the benefits of greenhouse gases by a group called CO2 Coalition.

Facebook, Microsoft, and Google were high-level sponsors of the conference. All 3 companies have previously pledged to reduce carbon footprints and pursue renewable energy sources, according to the letter sent by the congresswomen Monday.

“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.”

Though the congresswomen focused the letter solely on one event the conference hosted, there were others examining other areas of climate change, such as if carbon taxes are viable.

Facebook pointed to a 2017 blog post about the company’s political engagement and to the company’s sustainability policies in a statement about the letter to CNBC Monday.

Google and Microsoft did not immediately respond to requests made by Business Insider Monday.

Microsoft spokesman Frank Shaw posted a statement on Twitter Monday, saying, "Microsoft's engagement with LibertyCon was through a breakfast reception for student leaders to discuss topics including rural broadband and privacy." The statement also said, "Climate change is one of the most important issues of our time."

When news of the sponsorships emerged last week, a Microsoft spokesperson told The Verge that the company's "commitment to sustainability is not altered or affected by our membership or sponsorship of an organization." A Google spokesperson also told The Verge its sponsorships "doesn’t mean that we endorse the organization’s entire agenda or agree with other speakers or sponsors.”

The letter from Representatives Ocasio-Cortez and Pingree concluded: "Today’s coordinated campaign to deny climate change, or to put a positive spin on its effects, is not unlike that of the tobacco companies which once sought to discredit their product’s link to cancer. Their propaganda kept the nation from addressing a public health crisis for years, leading to many preventable deaths. We cannot afford to make the same mistake again with climate change."

Ocasio-Cortez is currently spearheading the Green New Deal — a bill that has brought climate change into national conversation as it aims to prevent the world from warming no more than 2.7 degrees Fahrenheit by 2100.