ExxonMobil gave more than $2.3m to members of Congress and a corporate lobbying group that deny climate change and block efforts to fight climate change – eight years after pledging to stop its funding of climate denial, the Guardian has learned.

Climate denial – from Republicans in Congress and lobby groups operating at the state level – is seen as a major obstacle to US and global efforts to fight climate change, closing off the possibility of federal and state regulations cutting greenhouse gas emissions and the ability to plan for a future of sea-level rise and extreme weather.

Exxon channeled about $30m to researchers and activist groups promoting disinformation about global warming over the years, according to a tally kept by the campaign group Greenpeace. But the oil company pledged to stop such funding in 2007, in response to pressure from shareholder activists.

"In 2008 we will discontinue contributions to several public policy groups whose position on climate change could divert attention from the important discussion on how the world will secure energy required for economic growth in an environmentally responsible manner," Exxon said in its 2007 Corporate Citizenship report.

But since 2007, the oil company has given $1.87m to Republicans in Congress who deny climate change and an additional $454,000 to the American Legislative Exchange Council (Alec), according to financial and tax records.

In a statement to the Guardian this week, Exxon spokesman Richard Keil reiterated: "ExxonMobil does not fund climate denial."

Alec, an ultra-conservative lobby group, has hosted seminars promoting the long-discredited idea that rising carbon dioxide emissions are the "elixir of life", and was behind legislation banning state planners in North Carolina from considering future sea-level rise.

Campaigners said Exxon's support for members of Congress and lobby groups that deny climate change was at odds with the company's public position that it is committed to acting on the threat posed by global warming.