In 2005 Judge Richard Mawrey voided the elections of six Muslim Asian councillors in Birmingham. He didn't have any faith in the ability of the police to deal with electoral fraud.
In his judgement Mawrey said:
147. Quite apart from the lack of training, there is a marked reluctance on the part of the police to involve themselves in electoral matters. If they are presented by somebody else with hard evidence of fraud, they will investigate but they tend not to go out of their way to look for it.
148. This is not helped by the invidious position in which a police force is put when investigating electoral fraud in a local authority context. The alleged fraudsters may, after all, be members of the political authority to which the force is answerable. The noble cop who fights corruption at City Hall at risk of his career may well be a staple of Hollywood movies but he is much rarer in real life.