G8 leaders must demonstrate much greater political courage on climate change or they will condemn today's Major Economies Forum declaration to being little more than hot air, Christian Aid warns.

Statements by the G8 so far - on trying to limit the global temperature rise to 2oC degrees and on cutting rich countries' emissions by 80 per cent by 2050 - are so vague as to be almost meaningless.

'G8 leaders have undermined their climate credibility by failing to adopt an emissions target for 2020 - or indicating how they will help developing countries meet the proposed temperature goal and global emissions target,' said Dr Alison Doig, climate policy expert at Christian Aid.

'With less than six months to go before the critical UN climate summit in Copenhagen in December, the world urgently needs more courageous political leadership.'

An early draft of the MEF declaration put a figure ($400m) on financial support that rich countries would give developing countries. 'While it was a start, it was not ambitious enough,' adds Dr Doig.

'Until world leaders commit themselves to mid-term targets on emissions cuts and financing, then negotiations towards a new global climate treaty are doomed,' she warns.

'Mid-term targets are essential because they require governments to take action on emissions relatively quickly. Targets set for 2050 are easy to dismiss because today's leaders will not be held accountable for meeting them.'

India and China are often blamed for stalling the negotiations but there is good reason for their reluctance to commit themselves. There has been little evidence of industrialised countries taking more than a minimal cut in their domestic emissions - offers on the table amount to a cut of only 14 per cent by 2020 from 1990 levels - and there has yet to be a serious offer of new finance for action in developing countries .

However, Dr Doig welcomed the draft declaration's acknowledgement that climate change 'poses a clear danger requiring an extraordinary global response...[which] should recognise the priority of economic and social development of developing countries'.

'Climate change is indeed a global emergency, and one for which rich countries are overwhelmingly responsible,' she says. 'It is also a global injustice, because it is poor people who are suffering the worst consequences -droughts, floods, and other extreme weather events which exacerbate hunger, disease and poverty.

'The Copenhagen summit is a major opportunity to help right that injustice and to avert climate catastrophe for the whole world. We need the leaders of the Major Economies Forum to lead the way now.'