Onshore wind and solar power farms in Buckinghamshire could fuel more than a million homes, according to new research.

Estimates from the National Grid suggest the UK must double the amount of renewable electricity it produces over the next six years to replace energy phased out from fossil fuels.

Climate and energy charity Friends of the Earth has called on all political parties to pledge to lift restrictions on onshore wind farms.

The campaign group said the Conservatives' track record on energy security is "woefully inadequate", and labelled Labour "increasingly shaky on climate" after it cut its £28 billion green investment pledge by half in February.

It has also urged local authorities to identify suitable renewable energy sites in local plans, and called for further investment in the electricity grid as a "top infrastructure priority".

Research conducted by Exeter University's Environmental Intelligence Centre and Friends of the Earth shows there is around 42 square kilometres of land in Buckinghamshire suitable for onshore wind farms.

There is also approximately 79 square kilometres capable of hosting solar power sites.

This would generate a total of 5,288 gigawatt-hours (GWh) of electricity, which would power around 1,958,600 homes based on average electricity consumption.

Researchers excluded higher-grade agricultural land, which can be degraded by solar farms, and implemented a one-kilometre buffer around all grade one and two listed buildings, a two-kilometre distance from any registered park or garden, and a 500-metre ring around any scheduled monument.

The research also excluded all national parks and areas of outstanding natural beauty, and did not factor in solar panels on roofs.

Tony Bosworth, climate campaigner at Friends of the Earth, said: "Unleashing the UK’s immense potential to generate cheap, clean homegrown renewables is essential to bring down our energy bills for good and meet the UK’s vital international target to reduce carbon emissions by two thirds by 2030."