The row over US inaction on carbon emissions reached new heights yesterday after the White House allowed Congress to look at last year's government proposal to officially deem climate change a threat to public health – a plan that aides to George Bush refused to acknowledge or read.

The climate plan was finished in December by the US Environmental Protection Agency (EPA) in response to a supreme court ruling that required the Bush administration to state whether carbon emissions should be regulated to protect public health.

The EPA concluded that regulation was needed, but whistleblowers have revealed that the White House ordered the agency to scrap its proposal. Democratic attempts to investigate the backroom dealings were stymied until this week, when senators were finally permitted a look at the plan.

The chairman of the Senate environment committee, California Democrat Barbara Boxer, released a summary of the proposal to reporters. Boxer was allowed to take notes on the plan but not given a copy.

"Based on the evidence before him, the [EPA] administrator believes it is reasonable to conclude current and future emissions of greenhouse gases will contribute to future climate change," the proposal stated.

"The US has a long and populous coastline," the EPA continued. "Sea level rise will continue and exacerbate storm surge flooding and coastline erosion … in areas where heat waves already occur, they are expected to be more intense, more frequent, and longer-lasting."

The EPA proposal also predicted that warming temperatures would lead to more wildfires in western US states and "additional strain" on already overtaxed water resources in the dry south-east and western regions.

Democrats asked the EPA administrator, Stephen Johnson, to testify next week at a hearing exploring allegations of White House obstruction on climate change. But Johnson refused, citing executive privilege and forcing the cancellation of the hearing.

"The American people are poorly served by an administration whose head of environmental protection cannot appear before a Senate committee and honestly discuss what he did and why he did it," senior Democrat Patrick Leahy said.

The next step may be holding Johnson in contempt of Congress, which would effectively move the dispute into the judicial system. White House chief of staff Josh Bolten and former Bush counsellor Karl Rove were found in contempt last year after refusing to cooperate with a different investigation, but their case has yet to move forward.

Boxer decried the White House's decision not to release the full EPA proposal to the public.

"It is clear. It is chilling. It is detailed," she said to colleagues yesterday. "That information belongs to the American people and we must get it to them. Then they will decide whether we should act to prevent this coming crisis or sit on our hands."

The EPA attempted to downplay the controversy in a statement to the Washington Post that called the proposal "a pre-decisional draft document" and "nothing new".