Companies are sitting on Australian coal resources likely to generate an extra 150 billion tonnes of greenhouse gases, setting a potential collision course with international efforts to curb global warming that would strand investments.

A report finds investments in new Australian coal, oil and gas projects are being made without regard to risk that they will later be devalued as the world moves to cut emissions.

The report by the British-based Carbon Tracker Initiative and the Australian Climate Institute says companies listed in the top 200 on the Australian stock exchange spend $5.7 billion a year developing and replacing coal reserves.

It says these reserves will largely need to be left untapped if global warming is to be kept at safe levels.

Climate Institute chief executive John Connor said investments in Australian coal ''rest on a speculative bubble of climate denial, indifference, or dreaming''.