It doesn't take a political genius to work out the consequences of allowing political parties to scrutinise applications for postal votes. Within a given district or ward, political parties are well aware of the likely levels of support both for themselves and for their opponents and equally that, if denied a postal vote, a proportion of those applicants will ultimately not vote at all. Far from scrutinising applications in the interests of preventing fraud, which is of course in the public interest, its inevitable that political parties will use the scrutiny process in their own interests by seeking, wherever possible, to depress the turnout in areas where they know their opponents are strong. It's a system that's intrinsically open to abuse and, frankly, crying out to be 'worked' for every political advantage it could possibly yield which mean, inevitably, that that is exactly what will happen.
How does he think parties will be able to depress turnout? The only way would be by pointing out that some postal vote applications are invalid - either the applicant is not entitled to vote, or the application has not been made by the ostensible applicant. In either of these cases identifying the problem would be a good thing.
This is an instance of the general fallacy of the undesirability of "partisanship" or "adversarialism". If something should be found out, the best person to find it out is the person with an interest in it being found. A neutral party is needed to decide whether the accusation is justified, but the neutral or disinterested cannot be trusted to make proper
The strength of our voting system is not that it is in the hands of the disinterested, but that it is visible to every interested party, who can verify that they are being treated fairly. The problem with postal voting is not that there are fewer "official" checks, but that it takes the whole process out of public view, where interested parties can no longer exert oversight. Whatever his
motives or faults, Hemming is right to attempt to repair that.