The progressive vote will be systematically ‘split’ in next week’s council elections because of the winner-takes-all electoral system, campaigners say.

The Politics for the Many campaign has warned that the First Past the Post system gives the right an advantage in local elections and forces people on the left to vote tactically.

Using data collated by Democracy Club, Politics for the Many found that in 43.8% of wards, there is one unified 'right' party (the Conservatives) standing candidates against all three of the progressive 'left' parties (Lab/Lib Dem/Green).

There are a further 35.5% of wards where there is one 'right' party (the Conservatives) standing candidates against two of the largest 'left' parties (either Labour, the Lib Dems or the Greens).

In 81.7% of wards, there are more 'left' parties standing candidates than 'right' parties. There are only 15 wards in the whole of England (0.5% of wards) where there are more right parties standing than left parties.

Nancy Platts, coordinator of the Politics for the Many campaign, said: ‘We’ve seen all too many times how our voting system serves as a barrier to progressive change, amplifying the votes of some while casting others on the scrap heap. The result – a winner-takes-all system that gifts unearned majorities to the government of the day. Governments that are all too often conservative.

‘It’s a system that forces voters to vote tactically, often supporting the ‘least worst’ candidate in order to try and game the broken system. In these local elections the odds are once again stacked against progressives and the results will likely reflect that in seats up and down the country.’