Labour challenged the Tories over their plans to take unilateral UK action on carbon emissions from aviation by introducing a system of personal air mile allowances for travellers.

Mr Brown instead focused on the need for European and wider international action, as well as a drive to make all homes energy efficient in the next 10 years. He also pledged to phase out old-fashioned light bulbs by 2011, in line with an EU heads of government decision last week.

The Tories said Mr Brown was simply recycling policies he had first announced in a speech in March 1995.

London and other big cities risk a food crisis because they are too dependent on imported produce grown using chemicals, Britain's leading organic farming pressure group will warn this week.

The Soil Association will mark its 60th anniversary by holding its annual conference in London to draw attention to what it calls the 'crisis' of feeding cities, which use up 75 per cent of the planet's environmental resources. The choice of London is, it believes, a way of reaching beyond its farming base to urban dwellers. 

The Ecological Footprint is a measure of the "load" imposed by a given population on nature. It represents the land area necessary to sustain current levels of resource consumption and waste discharge by that population. 

The association has calculated that London uses the environmental resources of an area 120 times its own size - equivalent to all the productive land in Britain. Thus its 'footprint' on the planet is far larger than its actual size. The biggest drain is the appetite of most of London's 7.5 million inhabitants for food grown with chemical fertilisers and pesticides, produced with great quantities of fossil fuels. Another key issue is that 80 per cent of the capital's food is imported, which uses even more barrels of oil. 

This makes London and other major conurbations 'extremely vulnerable' to a rise in fuel prices or any extensive disaster, from hurricanes to a bird flu pandemic, which would cut off supply chains, said Peter Melchett, the Soil Association's policy director. 'London is typical of large cities around the world,' he said. 'Behind the complacency of attitude stemming from over 50 years of global trade in cheap, anonymous food lies a chilling reality. If oil became really scarce or expensive, or global conflict reduced food availability, most of the world's cities would reach crisis point within weeks.'

Second National Councils Climate Conference - the Nottingham Call With international attention focused on climate change, local authorities in the UK have risen to the challenge of taking action at a local level. Local authorities play a pivotal role in meeting national objectives for reducing greenhouse gas emissions and in adapting to the impacts of climate change at a local level.  Over 200 delegates attended a conference in Nottingham on 5th December to re-launch the "Nottingham Declaration" which commits signatories to work at a local level to support the delivery of the UK Climate Change Programme, the Kyoto Protocol and the target for carbon dioxide reduction by 2010. Signatories also pledge to develop plans with partners and local communities to progressively address the causes and the impacts of climate change, according to local priorities and securing maximum benefit for local communities. 

100 local authorities have now signed up to the declaration - and the aim is to double that number within a year. All local authorities are invited to sign up to the Declaration and commit to working to address the causes and impacts of climate change.   Sign Up To Take Action Now.

For further information on how to sign up to the Nottingham Declaration visit  www.nottingham2005.org or contact info@lga.gov.uk