It is hoped that through the scheme, savers will feel they are helping to combat the effects of climate change as well as encouraging corporations to do more for the environment.

GISAs would enable savers to exceed the current £7,000 savings threshold that applies to standard stocks and shares ISAs, providing any additional investment falls into the ‘green’ category, which is likely to include Marks and Spencer, GlaxoSmithKline and BSkyB. According to reports, the new limit – which will be revealed today – could eventually be as high as £10,000 but is more likely to start at £8,000 or £9,000.

The party would introduce new rules to enable firms to be listed as ‘green’, including measures to curb emissions and use greener technologies. Mr Osborne says the GISA is “about creating a can-do culture on the environment, not a can’t-do lecture”, whereby individuals will “literally be able to save for the planet”.

The Conservatives are also set to create the world’s first Green Environmental Market (GEM), which will provide new capital and opportunities for green technology companies from the UK and worldwide. The GEM would sit alongside the Alternative Investment Market (AIM) and would allow investors to invest in environmentally friendly companies.

Mr Osborne believes the new trading market for green companies will “make the City of London the undisputed leader in green finance for years to come.”

© Fair Investment Company Ltd