Self assessment for dubious employment status

If an employer engages a worker under an arrangement that is 100% that of employment, but insists the worker is self employed, what does the employee need to do to ensure compliance?

I do not feel that registering as self employment is correct (as they are not self employed, despite what their employer might want), but as they know they aren't getting tax deducted at source, they therefore know they have untaxed income and thus have a liability to register under SA.

Would it be correct to therefore complete the employment pages and state no tax deducted, and give the employer's details? There is no PAYE scheme in place.

The employee wants to pay taxes due, but is more concerned with NI. They also want to keep their job.

I don't see any merit in shoe-horning this person into self employment in SA as they are just a worker, no real expenses, and indeed they are not truly self employed.

The correct answer is of course, "The employer needs to operate PAYE correctly" but this is not going to happen unless HMRC hit him with a big stick. There is no guarantee that shopping the employer will result in the use of said stick.

I am of course aware of MLR implications, I'm more concerned with the practical issues and how to protect the client.