Many of those denied a vote themselves have joined the outcry and taken to social media to highlight the often bizarre reasons given.
Here are seven of the most surprising:
‘Green Party supporter’
Ben posted a letter he received from Labour explaining the reason behind his membership denial.
In it, the note’s only reason given was: “You showed support for the Green Party on Twitter in 2014 and 2015.”
There was no further explanation or evidence of the posts, leaving Ben to brand the move “incredible”. He also shared comments on Twitter that criticised Labour for purging Green defectors rather than welcoming them.