A Democrat motion to block oil and gas extraction in a famed US nature reserve has been rejected in the Senate, giving oil companies the go-ahead to drill in northern Alaska.

The amendment, sponsored by Senator Maria Cantwell, would have reversed previous legislation that mandates the Senate Energy Committee to raise $1bn (£760,000) over the next decade - money which is expected to be raised by fossil fuel exploration.

The motion sought to protect the Arctic National Wildlife Refuge (ANWR), an area of outstanding natural beauty, which is home to polar bears, caribou and waterfowl.

However, big oil companies have long lobbied to explore the Alaskan site, as it is believed there may be 12 billion barrels of recoverable crude oil beneath the surface.

The motion narrowly failed by 48 votes to 52, with Senators divided mostly along party lines. Just one Republican, Senator Susan Collins of Maine, supported the measure.

Following the vote, Senator Cantwell denounced the Republicans “sneak attack” as an “attempt to turn over our public lands to polluters”

Environmentalists have vowed to continue the fight to protect the reserve.

Jamie Williams, president of the Wildlife Society, told Reuters: “Congress cannot sneak this through the back door when they think nobody is looking,” said Jamie Williams, president of the Wilderness Society.

“ANWR is simply too fragile and special to drill, and we have a moral obligation to protect it for future generations of Americans.”

However, Republicans in the area welcomed the news. Republican Senator Senator Dan Sullivan said in a statement: “This resolution is another key step that we’ve recently accomplished in a decades-long fight to allow Alaskans to produce energy in our state – something that Alaskans, Democrats, Republicans, independents, overwhelmingly support.

“More American energy production means more good-paying jobs, increased economic growth, and a stronger national security.”