Improving public transport is vital for tackling global warming, the Green Party has said.

Outlining its five election pledges on transport, the party said it was time to make Britain's cities cleaner and safer.

Principal Speaker Keith Taylor said that road pollution now accounts for more than one fifth of the UK's greenhouse gas emissions.

He blamed successive governments for "their neglect of the public transport network".

The Greens are proposing to spend £30bn on rail, bus, cycle and pedestrian transport improvements.

Other policies include renationalising the railways, re-regulating Britain's buses, and cutting car use by scrapping road tax but increasing fuel duty.

"A working, affordable public transport network is key to tackling climate change and to creating a more equitable society," said Taylor.

"The Green Party will implement five practical measures, to rebuild Britain's transport network, make cities cleaner and safer places, and reconnect rural Britain."