I spent some time recently at the three main party conferences. The issues of climate change and environmental sustainability were pretty close to the top of the agenda at all three. Interestingly, the parties have also begun to give more thought to the carbon footprint of these events themselves – the introduction of lightweight, sustainable security credentials being one of this year's favourite innovations! Walking around the stands at the exhibitions, I also had the impression that exhibitors were a little less likely to send you on your way with documents equivalent to a small forest, all nicely wrapped up in a branded plastic bag. Disposable bags – plastic and paper - are an interesting issue. Estimates suggest that every single adult in the country receives, on average, 220 disposable bags every year. Our conservative estimate is that Londoners use 1.6 billion of them - probably more. Only about 1 in 200 is likely to be recycled, so billions are going to landfill and many will take over 400 years to beak down. The government, working with retailers, is aiming for a 25 per cent reduction in the environmental impact of carrier bags by 2008. We welcome that, but we think there is a need to be more ambitious. We are asking Londoners whether or not they think a London-wide levy on throw away shopping bags should be introduced, or even an outright ban. Our tenth London Local Authorities Bill will be deposited in Parliament in November. Depending upon the consultation, we will include provisions to help London step up to the mark on this issue and show the sort of leadership that one would expect from a great, global city. In previous years, these London Bills have helped advance positions on big, topical issues. A previous proposal for a ban on smoking in public places in London was not successful, but it did help create the debate that culminated in the national legislation that took effect earlier this year. Creating that public debate – and we have had nearly 500 responses on shopping bags already – is a remarkably positive thing in its own right. It helps show that London's local authorities are not only shaping their own places, but together helping shape London as well. You can't do that without hearing from the public about how they want their places to be. This is a great opportunity for them to have their say. You can visit www.londoncouncils.gov.uk/thebigquestion John O'Brien is chief executive of London Councils