As a Muslim this is why I will not be voting in the forthcoming General Election in the U.K. on 12th December 2019:
It is haram.
Put very simply:
1) Legislation belongs to Allah alone and is sovereign.
2) Thus Parliament claims sovereignty and the only source of power to legislate.
3) Muslims must follow 1 not 2.
Sovereignty belongs to Allah. If we choose to give it to another by voting for an institution that claims a rival sovereignty (that can and does call black/white) are we not committing shirk?
Muslims of course are obliged to follow the law of the land – as long as it does not require Muslims to do prohibited acts such as eating pork.