As with many things, what we have now has come about by a corrupted cheapening of what we had before.
Imagine the traditional scenario of electrical contracting businesses, i.e. concerns with several employees, and NICEIC, the main player in the field of trade bodies for electrical contractors. (Despite what NICEIC say about their end customer focus they have always been a trade registration body.) It is, and always was, the business that was registered with NICEIC, and to be a NICEIC approved contractor a company had to have at least one Qualified Supervisor. There was a minimum ratio of QS:Non-QS employees, and there was a set of minimum qualifications that the QS had to have.
And basically he did, and was supposed to do, what it said on his tin - he was qualified, and he supervised the work of the work of others working for the same employer. It was the employer that was the registered Approved Contractor entity, and they were approved on the basis that they employed an appropriate number of appropriately qualified people to supervise the work done by the other employees.
It was not a case of people signing off work done by other people when they personally had not done the testing, it was a case of the company signing off work that the company had done. And the way that they did that, in principle, was the way that many many companies in all sorts of fields work - there are managers/supervisors in charge of/responsible for other employees, they and the company take their responsibilities seriously and put into place mechanisms to ensure the quality and trustworthiness of the employees, so that when Bill Installer went to Fred Supervisor and presented a set of test results Fred knew that Bill had done it properly and was happy to say that the company could issue the EIC. Part of Fred's responsibilities would have been to regularly trundle out on site some of the time and genuinely supervise the work being done by Bill.
Intrinsically there's nothing wrong with a system like that - nobody could imagine or expect, for example, that a new airliner from Boeing would get its certificate of airworthiness because one man had single-handedly done and checked everything, there would have been a huge hierarchy all down the line of companies saying "we are prepared to certify and take responsibility for XYZ" because they trusted their own employees and their organisation and supervisory regimes. There probably isn't a single identifiable person responsible for the actual design of even the khazi doors on a 787...
But back to electrical contractors and fast forward to 2005. Far from being dragged kicking and screaming, as TTC says, NICEIC and the ECA have been lobbying the Government for several years to impose statutory controls on who was allowed to do electrical work. It was sheer empire-building, self-aggrandising and commercial self interest at work. They'd seen what Corgi had done for the earning power of gas fitters and they wanted the same for electricians.
They didn't get that, what they got was Part P of the Building Regulations and the notification requirements. That none of it was based on a genuine safety need can be seen by even a cursory analysis of the figures in the Regulatory Impact Assessment done during the consultation period, and by the fact that kitchens are classed as special locations but utility rooms are not. Kitchen makeovers are very common, utility rooms much less so - there's a lot of work done by kitchen fitters in kitchens, not a great deal in utility rooms - we'll have the kitchen work please, don't care about utility rooms.
Anyone can see that from an electrical risk POV there is nothing to distinguish kitchens from utility rooms - it was all about economics.
Actually - what happened then is that there were some people dragged kicking and screaming - a number of self-employed electricians who'd never wanted to join NICEIC/NAPIT/ECA did resent being told that they had to, but mainly what happened was that NICEIC set about making plumbers and kitchen fitters and landscape gardeners etc members. Far from ensuring that only electricians did the electrical work in kitchens and bathrooms etc, they turned kitchen fitters and plumbers etc into "electricians".
To do that they took the Qualified Supervisor system, (which, while it hadn't been perfect and had in some cases resulted in shoddy work getting certified, didn't have any structural defects), dramatically lowered the standards for qualifications and experience needed to become a QS (so that all those other tradesmen could join the club and pay their fees into NICEIC's coffers), and created a type of "electrician" called a Domestic Installer. Most of those aren't properly qualified, aren't properly experienced, and I suspect that it's they, in the main, who are the ones signing off other people's work. Not necessarily because of venality, but simply because their own standards of knowledge and experience are so low that they figure everybody else's work must be OK because it's all so easy to do. If you take someone who already knows the difference between live & neutral and which end of a screwdriver to hold and after 5 days tell them "OK - you're an electrician now" they aren't going to regard it as a subject which requires a lot of knowledge and experience to get right.
And day after day, week after week, month after month, year after year we see people popping up here because they've hit something outside of what can be covered in 5 days and they haven't got a ******* clue.