The group is made up of 142 institutional investors overseeing more than €20 trillion (£17.9tn) in assets and includes HSBC, Allianz and JP Morgan.
Its letter says following changes to legislation governing carbon dioxide emissions from cars and vans, countries must react by supporting the development of low carbon technologies and fuels that can foster growth, boost jobs and improve public health.
The IIGCC claims mitigating climate change is essential for the safeguarding of investments.
The letter says the transport decarbonisation plan must be consistent with the EU’s 2030 and 2050 targets, as well as with the goals of the Paris Agreement and show strong ambition for new vehicle standards.
It suggests incentivising investment into cleaner transport and encourages more systemic disclosure of meaningful emissions data by manufacturers.