FAMILIES in an area of County Durham have the toughest challenge ahead to achieve the Liberal Democrats' dream of a "carbon-neutral" society.

Teesdale has easily the highest carbon emissions per person of any local authority in the United Kingdom, official figures show.

The average resident in Teesdale is responsible for pumping out 4.3 tonnes of carbon dioxide every year - compared to the national average of just 2.6 tonnes.

The figures, calculated for the department for the environment, food and rural affairs (Defra), were highlighted as Lib Dem delegates backed ambitious plans to make the UK carbon neutral by 2050.

The package - which the party insists is the only serious attempt to tackle global warming - would ban all petrol powered cars by 2040.

As well as hiking tax on gas-guzzling cars and charging lorries to use roads to double rail investment, it would also introduce 'green' mortages, to improve their energy efficiency.

That would seem to be a priority in Teesdale, where higher domestic carbon emissions must, at least in part, be the result of poorer home insulation.

The data was calculated from local electricity and gas meter readings and sales data, to measure energy use at the point of consumption, rather than generation.

Elsewhere in the region, there are also higher than average per-person carbon-emissions across most of North Yorkshire, perhaps reflecting greater use of electrical gadgets in wealthier homes.

Ryedale (3.4 tonnes), Harrogate (3.3), Craven (3.1) and Richmondshire (3.0) are all above the 2.6 national average, according to Defra.

In the North-East, Derwentside (3.4) also has higher emissions, but Middlesbrough (2.2) and Durham (2.1) are below average.

Yesterday, Chris Huhne, the Lib Dem environment spokesman, said urgent action was needed, because three-quarters of homes likely to be in use in 2050 were already built.

He highlighted how the average annual Swedish energy bill was £385 lower than in Britain - despite January temperatures being seven degrees centigrade lower.

Mr Huhne said: "At the moment, we might as well be standing outside our front doors, burning £50 notes."

The proposals were backed overwhelmingly by delegates, who rejected a call by Chris Davies, a Euro-MP, to end the party's opposition to nuclear power.