My brother works as a technician in a factory. For the past several months, he has been filling in a supervisor's job while they wait to recruit someone for it but he is not getting any additional pay for this. Isn't this against the law, to employ someone in a higher position and not give them the additional allowance for it?
Since your brother can do the job of the supervisor for so many months, why not ask his boss to promote him to be a supervisor rather than looking for another person? Hopefully he may get some salary increase. Try it, don't by shy about it. However, there is no law saying that the boss must give addition allowance. If your brother keeps quiet, the boss may also keep quiet about giving allowance.
KL Siew has put up a sister site by the name of mylabourlaw.net, which is in effect a more user-friendly version of the present popular pesaraonline.net. The site is in the process of being fine-tuned but it is fully functional. You are invited to visit the website at http://www.mylabourlaw.net and give your views or suggestions. Queries can be posted and be responded from there as usual.