Preventing tax evasion at the (alleged) cost of more lives lost is not a lot different - I think it is just semantics, though.
I think an argument (valid or not) against Part P is that it encourages people to neglect their electrical safety as Part P makes the cost of complying higher than many people wish to pay.
If the government paid all the costs of an electrician testing domestic installations + the cost of any remedial works for faults found, and paid you =A3100 for being a good citizen every time you requested such services, it would be very popular indeed. It would also be very expensive for the government, and therefore, us.
Part P was brought in on the (possibly spurious) grounds of improving the electrical safety of fixed domestic installations. The fact that it had the (offically) completely unexpected side effect of reducing tax evasion is (officially) neither here nor there, but the Treasury are not unhappy.
Just be glad that the European Court decided that we couldn't by toboacco and alcoholic beverages online and by mail order from other EU countries at their duty rates today. If the decision had been otherwise, the government would have been looking at creative methods of filling a =A312 billion hole in the public finances.
Sid