I think you need some legislation that would cover all employees. Basically, the idea is to make it an offence to retaliate in any way against someone who raises concerns and to give them a safe place to go in addition to their management. They should go to their own management first, but there should be somewhere they can go if their management doesn't listen, or if the management starts to make reprisals, and raise it to another level. Ultimately, they should be able to go public if they're not getting due process and their concerns are not being investigated properly. That's what it would look like.
You need well-written, strong legislation, because the problem for a whistle-blower is that they're typically up against the full resources of their employer. If you look at government departments, they will give a blank cheque to the justice department lawyers to go and do what it takes to tie up this poor person in the courts forever. It's important that the legislation be well written and strong.