The Wave, a visual protest being organised by the Stop Climate Chaos coalition, promises to be the UK's biggest-ever demonstration in support of international environmental action to combat climate change.
The event is due to take place in London on 5 December 2009, ahead of the crucial United Nations Copenhagen summit.
Before the march, international churches' development agency Christian Aid will also be co-hosting an ecumenical service including the Archbishop of Canterbury, Dr Rowan Williams and the Catholic Archbishop of Westminster, Vincent Nichols.
Free Church and other faith representatives, who have been lobbying hard for action against global warming, will also be involved.
Participants will be encouraged to dress in blue to "flood the streets of London and encircle Parliament to press home the need for the Britain to do all it can to seal a just deal in Copenhagen," say organisers - who are stressing the peaceful and friendly nature of the demo.
The Coalition wants the UK government to focus on three policy areas.
First, to end Britain's reliance on dirty coal power and instead boost the renewable energy supply to help build a green economy and create new jobs.
Second, to provide resources to help the world’s poorest and most vulnerable people adapt to climate change and allow them to develop in a carbon friendly manner.
Third, to deliver a fair global deal in Copenhagen that will keep global warming under 2 degrees C.
Christian Aid is also urging people to buy a Christmas charity gift that will help families living through the effects of climate change. Appropriate gifts include flood and disaster kits.
"If a group of friends or colleagues join together it would be possible to buy a bridge and help an entire community," the NGO adds.