By Roger Harrabin
BBC Environment Correspondent
The UK government publishes a review of its climate strategy next week. Labour's stated aim is to cut carbon dioxide (CO2) emissions by 20% from 1990 levels in the next four years.
It has made this CO2 pledge in three manifestos; but government insiders say tough decisions over emissions cuts have been delayed so long that the target is now virtually impossible to reach.
BBC News understands that the Prime Minister still has not resolved an inter-departmental dispute over the size of the central pillar of the CO2 strategy - the EU emissions trading scheme (EU ETS) for big business.
The Department for Environment, Food and Rural Affairs (Defra) wants companies to cut CO2 emissions by eight million tonnes over the period of the scheme's next phase; but the Department for Trade and Industry wants a three-million-tonne cut, to protect firms' competitiveness.
Many think the EU ETS offers by the far the biggest and surest CO2 savings, because the scheme is impossible for firms to dodge and because its effects can be precisely assessed.
The lack of clarity on it means the government has little idea how close it will get to its 20% commitment.
A Downing Street spokesman said 20% was still the target but declined to confirm whether or not numbers in the strategy would add up to 20.
If they do not, opposition politicians will accuse Labour of incompetence and lack of will. Anger will be directed at the Prime Minister who has said regularly climate change was the most important issue facing the planet.
Mr Blair will draw more fire because he plans to be out of the country when the climate policy is unveiled.
Critics will accuse him of preferring international exhortation over domestic action to reduce emissions. In his term of office, the UK's emissions of CO2 have risen by 1.9%.
That leaves the UK currently just 5.6% below 1990 levels - way off target.
If the government fails, it will have an international impact because other nations are watching to see if Mr Blair's promised leadership on climate is politically and economically achievable.
American climate "sceptics" will say the failure shows Kyoto-style targets and timetables for cutting CO2 will not work. This will dismay many scientists who see the physical evidence of climate change pressing much faster than their worst predictions.
Privately, Defra officials say the government has collectively failed to make the mental and organisational leap that is needed for CO2 reductions to become an over-arching policy.
They cannot yet imagine how the current economic structure - run as a slightly modified business-as-usual approach - will be able to deliver the 60% CO2 cut the Prime Minister says is necessary by 2050.
A cross-party statement from the Conservatives, Liberal Democrats, Plaid Cymru, the Scottish National Party and the Democratic Unionist Party calls for the establishment of an independent commission to set binding annual targets to cut UK emissions year on year. NGOs and some backbench MPs believe the yearly targets should be 3%.
It asks the government to join a consensual deal to take the politics out of climate policy. The government has so far rejected their approaches.
In the meantime, the government's CO2 projections in its forthcoming strategy review will be treated with some scepticism by independent analysts.
Already there have been warnings that the CO2 savings from the government's recently announced biofuels obligation for vehicles may be overestimated by 100%. And the projected savings from new building regulations may be greatly overstated, too.
The UK is currently on track to meet its Kyoto commitment to reduce emissions of six different greenhouse gases by an average of 12.5% compared with 1990 levels over the years 2008 to 2012
The fall in emissions through the 1990s and early part of the 2000s was achieved at a time of strong growth in the UK economy
Carbon dioxide emissions have risen recently, largely due to increased burning of coal in power stations. This was prompted by a rise in the price of gas (gas is 'cleaner' than coal)
The Labour administration has stated in three election manifestos that it would like to see a 20% cut in CO2 emissions by 2010