Both Hillary Clinton and Barack Obama may be proposing cap-and-trade schemes designed to cut emissions by 80 per cent by 2050, but that has not stopped the two Democratic presidential candidates signalling their support for clean coal technologies this week, as they attempt to woo voters in coal-rich states.

According to Reuters' reports, Clinton told a rally in Clear Fork, West Virginia that she would support "some big investments" in carbon capture and storage technologies.

Her comments followed a speech last week at the state's capitol rotunda in Charleston where she said she understood how important coal was to West Virginia, adding that "Coal is not going anywhere for the foreseeable future".

Meanwhile, Presidential frontrunner Barack Obama also signalled his support for clean coal technologies, distributing flyers across Kentucky stating that " Barack Obama believes in clean Kentucky coal".

Observers said that the moves represented an attempt to woo voters in two states where the coal industry employs around 39,000 people.

However, environmentalists slammed the move, noting that in a week when both Democratic candidates had criticised rival presidential nominee John McCain for not going far enough with his strategy for cutting emission by 60 per cent by 2050, Obama and Clinton were voicing support for an untested technology which many green groups argue is undermining investment in renewable energy.

"There is no such animal as clean coal," Brent Blackwelder, president of the environmental group Friends of the Earth, told Reuters. "We shouldn't be placing our bets on coal to bail us out. We need to be looking at getting rid of coal plants."

However, the move is likely to be welcomed by many within the coal industry who have seen clean coal technologies emerge as a central plank in the Bush administration's climate change strategy, and are keen to see investment in the sector continue.

The White House has ploughed hundreds of millions of dollars into a series of demonstration projects designed to prove the viability of the technology. Only last month the Department of Energy pledged to invest a further $126m in two projects to test the viability of geological formations as potential carbon sinks.

Advocates of the technology maintain it would allow the US to continue to tap into its 250 years worth of coal reserves, while still curbing carbon emissions.