Is it legal for my employer to increase my workload without raising my salary?

Check your contract and the national law that governs it: in many countries it's not illegal to increase your duties without raising your pay - it depends on how the agreement is written and what local regulations say. If your contract says your duties are "as agreed" or has a generic clause, technically they might have some wiggle room. But if there's a precise description of your role and tasks, drastically adding new ones without compensation could be a violation.

The concrete move is to document everything: keep track of what you're assigned, when, and how much time you spend on it. Then talk directly with your boss or HR, explaining that your workload has increased significantly. A lot of times it's organizational incompetence rather than malicious intent, and raising the issue formally often does the trick. If nothing changes, consult a labor lawyer in your area or your union (if you're part of one): they'll know exactly what's legal in your country and can advise you on whether you're entitled to a salary review or if you can file a formal complaint.

It really depends on where you work and how your contract is structured. In Italy, for example, your employer can't assign you duties that are completely different from what's laid out in your contract without your consent - if they do it illegally, you're entitled to compensation. But if the new duties fall within your contractual category (like if you're an employee and they're giving you more responsibility as an employee), technically it could be legal even without a raise, even though it's annoying.

What you should do is take a good look at what your contract says about your role and duties. If you see they've added tasks that go beyond the original description, document everything - emails, messages - where you ask for clarification and remind them what the original agreement was. At some point, if they keep ignoring you, it's worth talking to a union rep or a labor lawyer in your area, because laws vary from place to place.

A friend of mine was in exactly this situation a few years back: they basically promoted her but her salary stayed the same. She documented everything and then contacted the union, and they helped her negotiate a pay adjustment. It wasn't easy, but at least she got recognition for her work. In your case, before you take action, gather your documents and evidence of what they're asking you to do now versus before.