It comes as Jeremy Corbyn supporters makes claims of a “rigged purge” ahead of this month’s party leadership election.
The Nottingham punk duo have been vocal in their support for Jeremy Corbyn, who is currently fighting to remain Labour leader in the face of a challenge from Owen Smith.
However, Williams is the latest in a string of Labour Party supporters and members who have been banned from voting in the leadership contest because they do not “share the aims and values of the Labour Party.”
Williamson called the Labour Party “absolute scum” for its decision, which he also described as “weak”.
Allies of Corbyn have claimed that there has been a “rigged purge” of his supporters, leading to some being “unfairly” barred from voting in the leadership election, which is taking place until September 21.
Sleaford Mods last week announced a new five-track EP called ‘TCR’, set for release on October 14.