International advocacy group Oceana has reported an increase in opposition to controversial seismic airgun use along the East Coast, with the joining of 110 local elected officials and 155 conservation and animal welfare organisations to the mounting opposition against its use.

Six coastal towns have also passed local resolutions opposing the use of the technology.

In February, the US government released a final proposal allowing the use of the seismic airgun technology to look for oil and gas deposits deep below the ocean floor in an area twice the size of California, stretching from Delaware to Florida.

The Department of the Interior (DOI) said that the dynamite-like blasts could lead to injuries and possibly kill up to 138,200 marine mammals, such as dolphins and whales.

"Six coastal towns have also passed local resolutions opposing the use of the technology."

Local officials from Maine to Florida have raised concerns that the use of airguns threatens fish populations and profitable fisheries, and its noise has been shown to decrease catch rates of certain fisheries.

Various conservation and animal welfare organisations sent a letter stating that seismic airgun testing is the first step towards deep-water drilling, the same practice that caused the Deepwater Horizon oil spill disaster.

The conservation and animal welfare organisations include Oceana, Surfrider Foundation, International Fund for Animal Welfare, National Resources Defense Council, Clean Ocean Action and Southern Alliance for Clean Energy.

Oceana campaign director Claire Douglass said: "Offshore drilling is no safer than it was four year ago, yet President Obama is taking steps to expand this dirty and dangerous industry to the Atlantic.

"If the president would simply stop to listen, he would hear that coastal communities have no interest in turning the East Coast into a blast zone."

Seismic airguns are said to be loud enough to kill small animals at close range, and can disrupt the behavior of large animals such as whales and dolphins from up to 100 miles away.