HR Question?

I am a secretary and three years ago my company was making people redundant and also accepting voluntary redundancy. At that time my boss resigned and my department was reorganised leaving me in effect without a job. I asked to take voluntary redundancy but the company refused and put me in a position on a lower grade and my salary has been frozen ever since. My salary has been frozen as it is at the top of the scale for this lower grade and I have to wait for people to catch up. Unfortunately at the time I did sign a letter to accept the new position, but I just want to to clarify that a company can legally freeze your salary and put you on a lower grade just because somebody else has left the company? I suspect because I signed the letter they can, but morally I think it stinks.

Perfectly legal.

They are your employers, you are hired under their terms and conditions, which include Salary rate. If they revise your figure and it is lower than your former and you accepted by signing the Contract Amendment, then the contract is legally binding.

If you do not agree, then the contract is recinded and you can leave, or be summarily dismissed on grounds that no contract exists.

May I suggest possibly talking to the superiors (Your new line Manager) about how valuable you are to the company, and that you do think the salary deduction is a little unfair to you after your long service to the company.

You say your company was making people redundant. What do you mean? Were they cloning people or something? Why would you volunteer for that?
You just described communism.
One thing you can do is to leave. That is the beauty of Capitalism.
unless they did blatant discrimination (race, creed, color, age, sex, disability, etc) they are the employer, they pay your salary, you are out of luck. If you don't like your pay, find another job. Brutal, but that's the way the world is today unfortunately.