By Richard Black
Environment correspondent, BBC News website
E.On's Kingsnorth plans have led to protests at the existing plant
The government should set a deadline for coal-fired power stations to adopt "clean" technologies or close, according to a parliamentary committee.
The Environment Audit Committee says the government is wrong to believe that a carbon market alone will persuade companies to invest in "clean coal".
Its report warns that progress in this area is "extremely disappointing".
A coal-fired station produces about twice as much carbon dioxide as a gas-burning facility of equal power.
The company E.On recently won approval from Medway Council for plans to build new coal-fired plant at Kingsnorth power station in Kent, though a government decision on the project was recently postponed.
The committee heard evidence that five or six other new coal-burning stations may be built in the UK by 2015.
As gas prices rise, generators are increasingly looking to coal as a cheaper and more reliable alternative.
The UK government believes - as do others - that the answer is "clean coal", particularly technologies which capture carbon from the flue gases and store it away in natural underground voids, perhaps under the sea bed.
But the technology is expensive and makes a power station less efficient, increasing the amount of fuel burned by 10-40%.
Uncertainties about technical and economic aspects of clean coal mean it can be a "fig leaf", the committee warns, allowing government to claim it is developing a low-emission energy future when in fact there is no certainty that CCS will be introduced.
"Unless there is a dramatic technological development, coal should be seen as the last resort, even with the promise of carbon capture and storage (CCS)," the report concludes.
The government believes the EU Emissions Trading Scheme (ETS) will give companies an economic incentive to invest in CCS when the carbon price rises sufficiently.
Statoil's Sleipner plant is the world's first commercial carbon burial plant
But the Environment Audit Committee heard Energy Minister Malcolm Wicks admit this may not happen.
"We cannot afford to develop new coal-fired power stations when we have no guarantee about when they will be fitted with CCS, if at all," said committee chairman Tim Yeo MP.
"It is absolutely crucial for the government to... tell the industry that carbon capture and storage will be required, and that coal-fired power stations will not be permitted to operate unabated."
The committee says the government must set a date by which companies must have adopted CCS, or face closure of their installations - though it does not suggest which date should be adopted.
Responding to the report, Mr Wicks suggested the EU ETS would be enough to drive investment provided that national caps on emissions are tightened rapidly enough to give carbon a high price.
"The key is to get the level of the cap right," he said.
"The government supports current proposals for the cap to tighten year on year from 2013 - by 2020, the cap would be 21% below 2005 emission levels."
The committee also had harsh words for the government's decision to fund a single CCS demonstration facility when several competing technologies could all benefit from investment.
The Royal Society, the UK's principal scientific academy, endorsed the committee's call for bold leadership, but said the government "appears paralysed".
"The solution is straightforward; consent must only be given for new coal-fired power stations on condition that operating permits are withdrawn if the plant fails to capture 90% of its CO2 emissions by 2020," said the society's president Martin Rees.
Environment groups which are campaigning against the new Kingsnorth units were more outspoken.
"The government should not be relying on CCS - an unproven technology - to justify new coal power stations," said Tim Jones, climate policy officer with the World Development Movement.
"If the government goes ahead with new coal power without CCS, it would be setting the UK firmly on the path of high carbon emissions without a clear end in sight."