Nearly 20 million people live in the local government equivalent of 'One Party States', according to the Electoral Reform Society.
The Society said that over one in three people live in authorities without a viable opposition, which fails the basic test of democracy. In England and Wales, 104 authorities now have a single party holding in excess of 75% of council seats.
Darren Hughes, director of campaigns and research at the Electoral Reform Society, said: 'Any decent democracy requires a viable opposition. But in the One Party States of England and Wales nearly 20 million people don’t enjoy that luxury. These authorities enjoy power without real accountability – and council tax payers deserve better.
'We can’t rely on governing parties to keep themselves in check. Our councils need a critical mass of opposition for basic scrutiny to work – and it’s what the public keep voting for. But our broken voting system is handing out fake supermajorities to parties out of all proportion to their real support.
'Quite simply no councillor and no council should be beyond the reach of voters.'
The Society is calling for England and Wales to abandon first past the post, which was adopted by Scotland in 2007
