When Laura Rennie was told that the cat she lost as a kitten had been found 18 years after it wandered off, she was overjoyed. An animal welfare officer turned up at her home to say the tabby had been located and traced to her, thanks to its microchip. Toby had been hit by a car, but was alive and at a local vet’s. Even if it were just to say goodbye, or take charge of his veterinary care, Ms Rennie would at least be able do the best for Toby.

What a wonderful story, you might say, and what great proof, as complaints mount over the compulsory microchipping of dogs which became law this week, that pet microchipping is a much-needed resource. Surely this heartwarming tale shows that microchipping will only help loving pet owners, while targeting irresponsible breeders and those guilty of neglect.

Well, not quite. When Ms Rennie, 39, from Glasgow, contacted the vet’s, she was told they couldn’t wait the 20 minutes it would take her to reach the surgery. They put the cat down. The Scottish Society for the Prevention of Cruelty to Animals later apologised, but its attitude seems to have been more than a little proprietorial. Welfare officers judged it would be too upsetting for the owner to see the cat.

So what, you may well ask, is the point of a pet microchip?

From 6 April, all dogs over the age of eight weeks are required to have microchips which hold the name and address of the owner. The act is retrospective, so nine million dog owners need to comply now and could be fined up to £500 if they don’t. The procedure involves implanting a sterile chip the size of a grain of rice between a dog’s shoulder blades. Plenty of vets believe doing this to very small breeds could be dangerous or even fatal, but the owner no longer has a choice.

There has been a lot of bluster from the charities who pushed for the law change. Once chipped, they say, if your pooch gets lost then the welfare groups or police will be able to scan him and return him to you. Aw! Microchipping a dog at the vet’s will cost only £20, they boast. Pets At Home has a special offer on microchipping at £10 until 15 April. Vets usually charge a consultation fee, however, on top of the fee for any clinical procedure, so they will no doubt start charging nearer £50 at some point. And less scrupulous vets may eventually take the view, as panic-stricken owners rush to comply, that since chipping is compulsory, like car insurance, they can charge what they like.

I should point out that my spaniel Cydney came chipped when I bought her, as did my thoroughbred horse, Darcy. Good breeders have been doing this for a while. But I do not believe the hype about obligatory chipping. Because as usual, all the good people in the world will abide by the new rules while the feckless and irresponsible will ignore them.

This will leave the authorities twiddling their thumbs but — and perhaps here’s the real point — with lots of new powers to use. Once your dog has been microchipped, police and animal welfare charities will be able to scan his chip if he gets lost, trace him to you, and prosecute you for letting him run off. Or if he looks thin after two days on the run, perhaps they will blame you for that.

The new regulations state that dog microchipping ‘will be enforced by local authorities, police constables, community support officers and any other person which the secretary of state may authorise to act as an enforcer’. The ‘any other person’ seems very likely to be the RSPCA, since the charity is the main animal welfare group the police calls on and the only one that regularly prosecutes. The RSPCA insists on its website that it will not be enforcing the new law, but it does add, somewhat ominously: ‘The RSPCA do scan every animal that comes into our care and will be using the new law in our enforcement work as it clearly links an animal with an owner who is responsible for his/her welfare.’

We know from experience what the RSPCA can do to caring pet owners in overzealous prosecutions. Look at what happened to the owners of Claude the cat, taken to hell and back because the animal hobby bobbies deemed their elderly cat too thin and matted.

I can see an argument for forcing breeders to chip puppies before sale. If an abandoned animal can be traced to the breeder, and they can give information about who they sold it to, one might trace the odd neglectful owner. But isn’t it more likely that idiots who buy a puppy and then tire of it will now simply decide to kill the dog and dispose of its body?

And what if a well-intentioned breeder mistakenly sells to an owner who seems legitimate but turns out to be uncaring? Is the breeder liable? Will breeders have to resort to extensive vetting procedures, including CRB checking, to ensure no puppy goes to a potentially abusive home?

Possibly. Because the true motive behind these reforms may well be a drive to restrict pet numbers, by making it too arduous and expensive to breed and even to own a pet. And that’s fair enough, if you are convinced that bringing into the world dogs which could possibly be harmed at some point is worse than breeding millions of animals to be slaughtered and eaten, I suppose.

I have accused the animal welfare lobby of trying to restrict pet ownership before, and they usually threaten to sue. That tells me I am touching a nerve. Tying pet owners up in expensive red tape is one way of stopping an awful lot of people, and certainly the poor and the elderly, from owning pets, if that objective floats your boat.

Of course, there are sensible animal lovers who hope microchipping will crack down on the horror of animal abuse. Abandoned dogs cost the taxpayer and charities £33 million a year, with 110,000 strays picked up off the streets last year. Yes, the new law in theory means microchips might let owners be traced and held criminally liable. But in practice, I don’t see the sorts of yobs who kick puppies down the stairs complying with red tape. Only the law abiders will be traceable. Only the law abiders will be prosecuted and fined.

Will we see families taken to court for neglect because they let their dog escape the garden, when in fact Oscar the cockapoo is a pampered little sod who can get through stock fencing? Again, this is not so farfetched, given that two owners were prosecuted recently for not cleaning their dogs’ teeth.

The RSPCA says if your dog isn’t on an approved database you could be served with a notice. You’ll have 21 days to chip, or you may be liable to pay a £500 fine and face criminal prosecution.

The practical and civil liberties problems seem endless. It also just feels like a blasted imposition for an Englishman to be forced to microchip his best friend.