Alexander said: "Climate change is today's crisis, not tomorrow's risk, and is already affecting millions of people in Bangladesh."
The minister praised the country's "innovative approach to adapting to the changing climate" but said "adaptation on the ground is not enough. We believe more must be done at a global level."
"This is why today the UK and Bangladesh are announcing a new partnership calling for a comprehensive deal in Copenhagen, leading to the stabilisation of greenhouse gases at a level that avoids dangerous climate change and benefits some of the world's poorest people," he said.
Many scientific experts argue Bangladesh is experiencing more rainfall, flooding and droughts, as well as cyclones as a direct result of global warming.
|Bangladesh says it needs huge amounts of money to ensure its survival [AFP]
Last year, widespread flooding and a devastating cyclone caused crop and infrastructure damage worth $2.8bn, around four per cent of Bangladesh's gross domestic product, according to a World Bank study.
AHM Rezaul Kabir, Bangladesh's environment secretary, said research by the bank, leading donors and the Bangladeshi government had found the country urgently needed huge amounts of money to ensure its survival.
He said: "We need at least $4bn at least by 2020 to build dams, cyclone shelters, plant trees along the coast and build infrastructure and capacities to adapt to increasing number of natural disasters."
Bangladesh says rich nations should pay the money needed as they are the biggest polluters.
Kabir said: "We hope Western countries will grant the money as compensation for being the biggest carbon emitters. They are responsible for our woes and the increasing number of the disasters that befall on us.
"In London, we will show where we are vulnerable and present our strategy to fight the greater number of floods, cyclones, a rise in sea levels crop losses."
Alexander said the $133m in aid would help Bangladesh "protect its people further from impacts such as rising sea-levels, water-logged land and increased salinity."
Earlier this year, the Bangladeshi authorities this year launched a $44m fund dedicated solely to fighting the problems that the country faces as a result of climate change.
The Nobel Prize winning United Nations Inter-governmental Panel on Climate Change predicts rising sea levels will devour 17 per cent of Bangladesh's total land mass by 2050, leaving at least 20 million people homeless.
James Hansen, director of the US-based NASA Goddard Institute for Space Studies, paints an even gloomier picture, forecasting the entire nation will be under water by the end of the 21st century.