I am indebted to the Construction Skills Register in Northern Ireland (equivalent to Construction Skills aka CITB) for coming up with a new spin on competence assessment in the form of the 24 hour NVQ.
This rather dubious concept was being made available to the construction industry in N.I. earlier in the year in the form of a pilot scheme for L2 NVQs for bricklayers, joiners and plasterers with a minimum of 5 years experience.
The promotional material states that 'the assessment process will take only a day or two at the most and will involve the following 3 elements: Discussion of relevent working experience; Practical task observed by approved assessor; Health & Safety touch screen test'
The piece concludes that 'qualifications such as an NVQ level 2 provide clients with confidence that companies have a skilled and qualified workforce' - words fail me.

International live demonstration show for the quarrying, recycling and heavy construction industries at Hillhead Quarry, Buxton, UK.
The monthly journal for the quarry products industry.
Comments
I understand this scheme is still very much in use with all those trades you mention plus glaziers [and probably more]. Like you, words fail me too.
Competence must be measured over time and thus demonstration of skills must be seen to be believed - and in the workplace.
I can see how a quick touch-screen test and 30 minute professional discussion could be used as one method of assessment of a skill - but not as the only method of assessment. And certainly not in one day. NVQ Assessment strategies usually state competence has to be demonstrated and measured over time... over time is not 24 hours.
It strikes me that this particular scheme doesn't measure competence at all, but does measure the applicants ability to blag! And the only person it cheats is the applicant themselves!
So much for a competent, safe and skilled workforce!
Of course the other complete downside to this scenario is that if NVQs can be done in a day, then the whole network of training providers is no longer required.
Until someone gets killed that is!
i completely agree the real measure of competency is in variety of experience,for instance i am a merchant seaman i have been fortunate enough to work on many varied projects within the shipping fields,the varyations in offshore work on small and large vessels is staggering one could not do a written test for this type of work ,also as a rigger onshore and in the petrochemical industries the different types of work experienced can only be hands on
Thats nothing! My Level 2 NVQ Quarry Machine Operative for wheel loader and dumper was done in a morning AND two of us did it at the same time. So called assessor turned up, told us answers for a question paper, took a few mocked up photos and that was it! According to my boss the cost was £1100 per employee and it was all funded by government. What a sham and an outrage that this is supposed to demonstrate competence.