The Prime Minister will make speech in Manchester tomorrow to mark the centenary of women winning the right to vote. If the advance reports are right, and judging from her Twitter feed today they appear to be, then she will also propose a change to the criminal law to offer candidates specific protection from abuse.

We all know the genesis of this idea. Graffiti, vile messages, intimidating behaviour and so on was far too common an experience at the last election. Many Conservative candidates were targeted in this way, as were various candidates of other parties. Plenty of activists have experienced similar abuse, and the attempt by masked thugs to disrupt a speech by Jacob Rees-Mogg on Friday is a reminder that such threats haven’t gone away.

In December, the Committee on Standards in Public Life recommended that “Government should consult on the introduction of a new offence in electoral law of intimidating Parliamentary candidates and party campaigners.” From the newspaper reports yesterday and today, it seems that Theresa May is minded to take up that proposal.

However, at best the idea is only superficially attractive.

The fact that even the Prime Minister’s own tweet (pictured, right) uses three different terms – “threats”, “abuse” and “intimidation” – interchangeably is a warning sign. Threats and intimidation are, rightly, already criminal offences in this country. “Abuse”, on the other hand, is an extremely broad term which could encompass such criminal behaviour but also is routinely used to refer to legal (if sometimes unpleasant) actions – like insulting or criticising somebody, with or without merit. Are

So far as I can see there are two possibilities as to how such a new law might work.

Perhaps it would restrict its scope to actions that are already criminal – the threats and intimidation – but offer additional, special legal protection to “Parliamentary candidates and party campaigners”, as the CSPL suggested.

But if the police already fail to protect candidates and activists from behaviour that is already illegal, will creating a new category for the same offences really make any difference?

And are there not obvious downsides to giving the impression that people involved in politics are an exalted and separate class, whom it is more serious to threaten or intimidate than a random passerby? That seems like a poor use of law, and a negative message to send to an electorate already disillusioned with what many see as a remote and self-serving political class.

Alternatively, perhaps such a new law might extend the scope of what is currently illegal, criminalising “abuse” of election candidates in addition to the above additional legal protection. That would be a dangerous restriction on free speech, and you can bet that it would instantly become a tool used by some in politics to silence robust but legitimate criticism by their opponents.

What does “abuse” mean? Would I be committing a criminal offence if I wrote that Jeremy Corbyn is a useful idiot of various tyrants and enemies of this country? How about if I shouted it at him at a public meeting?If a member of Britain First is standing for election, would it be a crime to call them “fascist scum”? Would it be illegal to say that Richard Burgon, the Shadow Justice Secretary, routinely gives the impression of being a man who could be easily outwitted by a revolving door? Should it really be a criminal offence to boo a Tory speaker at a public hustings? How about on Question Time?

Such laws are an obvious mire in the making. Worst of all, we might end up with one which adopts the flawed logic of existing hate crime legislation, which gives the power of judgement entirely to the person who claims to be a victim. Think about how much people dislike politicians right now. Then consider whether it will make them more or less popular if they are able to get people arrested and convicted simply on their say-so that someone was criminally rude to them.

If you’ve suffered abuse at the hands of political opponents, you might find such proposals tempting. But remember, laws cannot be designed on the assumption that those using them are good and reserved, and they will be available to your opponents, too. Jacob Rees-Mogg might use such power rarely, if ever, and with great care; Tulip Siddiq, who recently reported Channel 4 journalists to the police for asking her awkward questions, might not.

It’s only four years ago that the Conservatives changed the law in favour of free speech by reforming Section 5 of the Public Order Act, a bad law which previously outlawed “insulting” language. It would be deeply unwise to effectively reintroduce such an offence, only made worse by framing it as a privileged protection reserved only for politicians and their activists. By all means, enforce the current law; catch and punish those who threaten, terrify and harm. Expose those who sling abuse and act awfully, so that voters can pass judgement on them and those who enable them. But don’t get bogged down in trying to legally regulate political rudeness.